bug#15107: 24.3; replace-regexp-in-string wrong on \`

[Kevin Ryde <user42@zip.com.au>]

replace-regexp-in-string behaves incorrectly if a regexp has \` among
its matches.

    (replace-regexp-in-string "\\`\\|X" "Z" "--XX--" t t)
    =>
    "Z--ZXZX--"

where I expected

    "Z--ZZ--"

This seems to be due to the optimization in replace-regexp-in-string
which re-matches on the matched substring.  \' can match the substring
where it did not match in the middle of the full string.  In the example
above "X" is the match in the full string, but on taking that "X" as a
substring it can match "\\`".

Probably similar mismatches on the substring occur for things like \' ^
$ \b \< etc.  Maybe the comment in the code about munging the match data
would be a better way.





In GNU Emacs 24.3.1 (i486-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2013-05-29 on blah.blah, modified by Debian
System Description:	Debian GNU/Linux testing/unstable

Configured using:
 `configure '--build' 'i486-linux-gnu' '--build' 'i486-linux-gnu'
 '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
 '--localstatedir=/var/lib' '--infodir=/usr/share/info'
 '--mandir=/usr/share/man' '--with-pop=yes'
 '--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.3/site-lisp:/usr/share/emacs/site-lisp'
 '--with-crt-dir=/usr/lib/i386-linux-gnu' '--with-x=yes'
 '--with-x-toolkit=lucid' '--with-toolkit-scroll-bars' '--without-gconf'
 'build_alias=i486-linux-gnu' 'CFLAGS=-g -O2 -fstack-protector
 --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wall'
 'LDFLAGS=-Wl,-z,relro -Wl,-znocombreloc'
 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LANG: en_AU
  locale-coding-system: iso-latin-1-unix
  default enable-multibyte-characters: t