#4 Fix name clash with other zlib related apache modules

[arekm]

Apache was segfaulting frequently after loding mod_gzip.
That was due to name clash with other modules like
php-zlib.

Same symbol names in php-zlib and mod_gzip - that was
causing segfault in for example longest_match() from zlib
(instead of using mod_gzip version of longest_match zlib
version was used).

Fix is to make all mod_gzip_compress.c functions and
variables static (visible only to mod_gzip) and rename
gzp_main.

Attached patch fixes that. Tested.

[arekm]

Fix name_clash.