Add select() to Android bindings

It's tough to have PRs bounce or to have a back and forth with contributors
about minor style quibbles. Sometimes it ends up just being easier to fix style
after the fact, but let's add some automation to help this!

This commit adds a script to run on CI and locally to verify the style of this
repository. There's a few stylistic guidelines to ensure that definitions are
understandable across the jungle of modules. This consistency should help assist
readability for any future readers!

iOS was fixed awhile back and we should have rumprun nightlies now, so let's use
them!

Use nightlies for iOS and rumprun

This is how MetadaExt expects these fields to be named.

See https://github.com/rust-lang/rust/blob/c116ae35cf49b55bd8d82e31f1ba030cf7e63867/src/libstd/os/linux/fs.rs#L107-L121

Add SYS_gettid

The function is defined in POSIX [0], but according to Gnulib docs [1],
it is missing or not declared on at least some versions of OS X and
FreeBSD. On Solaris, it is not a system call but is present as
fdatasync(3) [2].

[0] http://www.opengroup.org/onlinepubs/9699919799/functions/fdatasync.html
[1] https://www.gnu.org/software/gnulib/manual/html_node/fdatasync.html
[2] http://docs.oracle.com/cd/E36784_01/html/E36874/fdatasync-3c.html

… merge

… merge

Conflicts:
	src/unix/notbsd/linux/musl/b32/arm.rs
	src/unix/notbsd/linux/musl/b32/asmjs.rs
	src/unix/notbsd/linux/musl/b32/x86.rs
	src/unix/notbsd/linux/musl/b64/mod.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

Merge a few PRs together