[gzip] Support `gzip' encoded header conditionally.

In order to support `gzip' encoded header the call to
`inflateInit2' was modified in commit 6a92b1fadde26477a9179.
However, this code breaks with the outdated internal version
of zlib.  This is a temporary fix to conditionally support
`gzip' encoded header whenever a system installation of zlib
is being used.

Problem report in


* src/gzip/ftgzip.c (FT_Gzip_Uncompress): Change the the call to
`inflateInit2' depending on whether the system installation is
being used or the internal copy.
2 files changed