bug#35241: 27.0.50; Tramp can't decrypt .authinfo.gpg in Win 10

[Shuguang Sun <shuguang79@qq.com>]

Hi,

I use .authinfo.gpg to store my login information, instead of .authinfo. 

Whe I open /plink:... with tramp, emacs get blocked and it seems tramp
is dealing with .authinfo, and it doesn't decrypt the file. I need open
.authinfo.gpg first, which means emacs can read .authinfo.gpg whithout
interaction (passphrase?), and then tramp can do the following action
(e.g., login...), and messaging 
"Decrypting c:/Users/username/HOME/.authinfo.gpg...done".

Gnus works well, and it can interact with passphrase and ask for the
password for .authinfo.gpg.


In GNU Emacs 27.0.50 (build 3, x86_64-w64-mingw32)
 of 2019-04-05 built on RSHMX11052
Repository revision: a68c96863289d5d8ccfc2f775d0018a2721c5e53
Repository branch: master
Windowing system distributor 'Microsoft Corp.', version 10.0.15063
System Description: Microsoft Windows 10 Enterprise (v10.0.1703.15063.1689)


Configured using:
 'configure --without-imagemagick --without-pop
 '--program-transform-name=s/^ctags$/ctags.emacs/'
 PKG_CONFIG_PATH=/mingw64/lib/pkgconfig:/mingw64/share/pkgconfig'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY W32NOTIFY ACL GNUTLS LIBXML2
ZLIB TOOLKIT_SCROLL_BARS THREADS JSON PDUMPER LCMS2 GMP

Important settings:
  value of $LANG: CHS
  locale-coding-system: cp936