bug#8655: 24.0.50; doc of previous-single-char-property-change

[Drew Adams]

Everything is symmetrical between the doc for
`next-single-char-property-change' and
`previous-single-char-property-change': last/first, forward/backward,
end/start... EXCEPT for this phrase, which is identical in the two doc
strings: "return LIMIT if nothing is found before LIMIT."
 
The problem is the ambiguity of "before".  Change the wording to "before
reaching LIMIT" and there is no problem.
 

In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2011-05-10 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.5) --no-opt --cflags
-Ic:/build/include'