bug#16292: 24.3.50; info docs now contain single straight quotes instead of `'

[Glenn Morris]

PS also note that vhdl-mode.texi does not contain @documentencoding.
I think it's a bit crap if we are supposed to remember to add this to
all new texi files, even if they have no real need for it.

(Presumably the fabulous info+.el is supposed to handle other info files
besides just those from Emacs, so it needs to handle this anyway.)