Remove `infback.c` which we don't need.
The `OF` macro was also removed so I can drop the patch where I yell
at Gentoo developers.
(cherry picked from commits e0e1f2e4a2056db1a908af75612daaaf5b129ebd
and 071499ac0d8e33e6f269437c3ce4fab52cc43f90)
Security update, fixes CVE-2018-25032 in zlib.
Preliminary assessment doesn't show Godot as affected since we don't
seem to call `deflate` with the problematic parameters, but the extent
of the vulnerability is not fully clear upstream yet.
- akien-mga
e1beca0232
