I just had a need to decode a piece of Zlib data from out of the

I just had a need to decode a piece of Zlib data from out of the
middle of a PDF. So here's a modification to sshzlib.c which enables
it to be compiled into a standalone Zlib decoder if you define
ZLIB_STANDALONE. As an added bonus, it (both standalone and in
PuTTY) also validates the Zlib header, just to make sure someone
hasn't defined a new compression format.

[originally from svn r4657]