Fix getgrgid_r to accept gid_t.

src/fuchsia/mod.rs

src/unix/bsd/mod.rs

src/unix/haiku/mod.rs

src/unix/newlib/mod.rs

src/unix/notbsd/android/mod.rs

src/unix/notbsd/linux/mod.rs

src/unix/solarish/mod.rs

src/unix/uclibc/mod.rs