Add more bindings for signals and select/pselect

libc-test/build.rs

src/dox.rs

src/lib.rs

src/macros.rs

src/unix/bsd/mod.rs

src/unix/mod.rs

src/unix/notbsd/android/mod.rs

src/unix/notbsd/linux/mips.rs

src/unix/notbsd/linux/notmips/mod.rs

src/unix/notbsd/mod.rs