bug#15606: 24.3.50; doc string of `replace-match-string-symbols'

[Drew Adams]

These are characters, not symbols.  This is Lisp, where "symbol" means
something quite different.  It is perhaps too late to name the function
correctly, but it is not too late to correct the doc.  Just replace
"symbol" by "character" everywhere.

Note that there are many occurrence of "symbol" in replace.el, but
fortunately the only incorrect occurrences are in
`replace-match-string-symbols'.

In GNU Emacs 24.3.50.1 (i686-pc-mingw32)
 of 2013-10-09 on LEG570
Bzr revision: 114596 jan.h.d@swipnet.se-20131009185014-vynfyw4o8p5fge54
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking 'CFLAGS=-O0 -g3' CPPFLAGS=-DGLYPH_DEBUG=1'