zlib: wrap remaining calls to direct inflate/inflateEnd

zlib: wrap remaining calls to direct inflate/inflateEnd

Two callsites in http-backend.c to inflate() and inflateEnd()
were not using git_ prefixed versions.  After this, running

    $ find all objects -print | xargs nm -ugo | grep inflate

shows only zlib.c makes direct calls to zlib for inflate operation,
except for a singlecall to inflateInit2 in http-backend.c

Signed-off-by: Junio C Hamano <gitster@pobox.com>