bug#31815: 27.0; Inappropriate use of curly quotes in `info.el'

[Drew Adams]

In `info.el' there are three occurrences of this (these are curly quotes,
in case that doesn't come through in the bug-report system):

  Index for '%s'

They were all changed from this text:

  Index for `%s'

The latter text should be restored.  There is no reason to burden these
contexts with those Unicode curly quotes.  That just makes it harder for
a user to save the buffer text, requiring her to use a Unicode-friendly
encoding.

NOTE: I searched the top level of the Lisp sources, and it appears that
this problem is present there only in `info.el'.  It might also exist at
levels below directory `lisp', so that possibility should be checked.

In GNU Emacs 27.0.50 (build 3, x86_64-w64-mingw32)
 of 2018-03-21
Repository revision: e70d0c9e66d7a8609450b2889869d16aeb0363b5
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install -C 'CFLAGS=-O2 -static -g3''