Fix SYS_gettid type to match first argument of syscall.

src/unix/notbsd/android/b32.rs

src/unix/notbsd/android/b64.rs

src/unix/notbsd/linux/mips.rs

src/unix/notbsd/linux/musl/b32/arm.rs

src/unix/notbsd/linux/musl/b32/asmjs.rs

src/unix/notbsd/linux/musl/b32/mips.rs

src/unix/notbsd/linux/musl/b32/x86.rs

src/unix/notbsd/linux/musl/b64/mod.rs

src/unix/notbsd/linux/other/b32/arm.rs

src/unix/notbsd/linux/other/b32/powerpc.rs

src/unix/notbsd/linux/other/b32/x86.rs

src/unix/notbsd/linux/other/b64/aarch64.rs

src/unix/notbsd/linux/other/b64/powerpc64.rs

src/unix/notbsd/linux/other/b64/x86_64.rs