bug#30670: 26.0.91; PNG files on Windows

[kensanata@gmail.com]

I can view JPG files but not PNG files on Windows and I don't know why.
I see that it's a configured feature in the output below but apparently
the right DLL is not included because 

(image-type-available-p 'jpeg) => t
(image-type-available-p 'png) => nil

This is what my bin directory contains:

c:/Portable Programs/emacs-26.0.91-x86_64/bin $ ls lib* | grep "png"
libpng-config
libpng16-16.dll
libpng16-config

Cheers
Alex



In GNU Emacs 26.0.91 (build 1, x86_64-w64-mingw32)
 of 2018-01-22 built on CIRROCUMULUS
Repository revision: 752fba992b793a74d202c9cfc3e1a92fd458e748
Windowing system distributor 'Microsoft Corp.', version 6.1.7601
Recent messages:
user-error: No window up from selected window
No IRC activity.
Saving file c:/Users/asc/AppData/Roaming/.emacs.d/url/cookies...
Wrote c:/Users/asc/AppData/Roaming/.emacs.d/url/cookies
Mark saved where search started
Mark set
Quit
user-error: No window right from selected window
user-error: No window up from selected window
Type C-c C-c or C-c C-x to view the image as text or hex.

Configured using:
 'configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS LCMS2

Important settings:
  value of $LANG: de_CH.UTF-8
  locale-coding-system: cp1252

Major mode: Dired by name

Minor modes in effect:
  diff-auto-refine-mode: t
  magit-auto-revert-mode: t
  global-git-commit-mode: t
  async-bytecomp-package-mode: t
  shell-dirtrack-mode: t
  rcirc-track-minor-mode: t
  electric-pair-mode: t
  winner-mode: t
  show-paren-mode: t
  ivy-mode: t
  global-git-gutter-mode: t
  global-company-mode: t
  company-mode: t
  cl-old-struct-compat-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow ecomplete mail-extr emacsbug sendmail image-mode dired-aux quail
shr-color vc-git magit-obsolete magit-blame magit-stash magit-bisect
magit-remote magit-commit magit-sequence magit-notes magit-worktree
magit-branch magit-files magit-refs magit-status magit magit-repos
magit-apply magit-wip magit-log magit-diff smerge-mode diff-mode
magit-core magit-autorevert autorevert filenotify magit-process
magit-margin magit-mode magit-git magit-section magit-popup git-commit
magit-utils log-edit pcvs-util add-log with-editor async-bytecomp async
markdown-mode rx noutline outline crm cus-edit cus-start cus-load
hippie-exp rcirc-late-fix pcmpl-unix mm-archive message rfc822 mml
mml-sec mailabbrev gmm-utils mailheader mm-decode mm-bodies mm-encode
iso-transl eieio-opt speedbar sb-image ezimage dframe find-func
tramp-cache tramp-sh tramp-cmds bs tramp tramp-compat tramp-loaddefs
trampver ucs-normalize shell hi-lock em-smart em-term term ehelp
em-script em-prompt em-ls em-hist em-pred em-glob em-dirs em-cmpl
em-basic em-banner em-alias esh-var esh-io esh-groups esh-help man dash
em-unix pcomplete esh-cmd esh-opt esh-ext esh-proc esh-arg eshell
esh-module esh-mode esh-util rect misearch multi-isearch conf-mode
epa-file epa epg colir help-fns radix-tree pp timezone parse-time
url-http mail-parse rfc2231 url-gw url-cache url-auth eww mm-url gnus
nnheader gnus-util rmail rmail-loaddefs rfc2047 rfc2045 ietf-drums
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emms-librefm-scrobbler emms-playlist-limit emms-volume easy-mmode
emms-volume-amixer emms-i18n emms-history emms-score emms-stream-info
emms-metaplaylist-mode emms-bookmarks emms-cue emms-mode-line-icon
emms-browser sort emms-playlist-sort emms-last-played emms-player-xine
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url-util mailcap emms-streams emms-show-all emms-tag-editor format-spec
emms-mark emms-mode-line emms-cache emms-info-ogginfo emms-info-mp3info
emms-info later-do emms-playlist-mode emms-player-vlc
emms-player-mplayer emms-player-simple emms-source-playlist
emms-source-file locate dired-x dired dired-loaddefs emms-setup emms
emms-compat server cl-extra help-mode network-stream puny nsm rmc
starttls tls gnutls rcirc-notify rcirc-styles rcirc-menu rcirc-color
color rcirc comint ansi-color bitlbee idle-highlight-mode
foggy-night-theme pink-bliss-theme session rcirc-emojis oddmuse-curl
derived goto-addr skeleton sgml-mode shr svg xml dom browse-url
elec-pair windmove winner paren ivy delsel ivy-overlay ffap thingatpt
image-file git-gutter advice company-oddmuse company-keywords
company-etags etags xref project ring company-gtags company-dabbrev-code
company-dabbrev company-files company-capf company-cmake company-xcode
company-clang company-semantic company-eclim company-template
company-css company-nxml company-bbdb company pcase authinfo edmacro
kmacro cl generic finder-inf info package easymenu epg-config
url-handlers url-parse auth-source cl-seq eieio eieio-core cl-macs
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byte-compile cconv cl-loaddefs cl-lib time-date mule-util tooltip eldoc
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ls-lisp disp-table term/w32-win w32-win w32-vars term/common-win
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode elisp-mode lisp-mode prog-mode register page
menu-bar rfn-eshadow isearch timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core term/tty-colors frame cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote w32notify w32 lcms2
multi-tty make-network-process emacs)

Memory information:
((conses 16 1581571 318634)
 (symbols 56 55840 4)
 (miscs 48 2805 2077)
 (strings 32 265387 22696)
 (string-bytes 1 7399673)
 (vectors 16 88791)
 (vector-slots 8 2410934 72882)
 (floats 8 483 1164)
 (intervals 56 156003 1226)
 (buffers 992 103))