In addition, move the syscalls to the mips module file because they are
all identical in mips32 and mips64.

As a result of this commit, glob64_t will be added to mips64.

MINSIGSTKSZ is a minimum size of process stack allowed

Having the B* constants in `unix/notbsd/mod.rs` passed CI tests
except for powerpc.  So we'll try moving into individual
arch/ABI that the CI tests cover for now. This commit should
pass for the following:

- mips32
- mips64
- musl32
- musl64
- android32
- android64
- arm32
- aarch64
- x86
- x86_64

Then we can figure out the powerpc variants.  This also prevents
potential errors for sparc64 which is not covered by CI.

MIPS32 and MIPS64 userspaces are mostly the same save the obvious ABI
difference, hence most of the const definitions could be shared.

This commit is not introducing any new significant additions, but mostly
just shuffles the existing files around to make the directory structure
more similar to the other, more mature platforms. The structs and extern
fn definitions are not touched. Plus a couple of new consts for MIPS64
to match MIPS32 coverage:

* `RLIM_INFINITY`
* `SYS_gettid`

Passed `libc-test` on Gentoo MIPS64el (n64 ABI), on a Loongson 3A2000
box. The test suite itself needs some more love to actually compile
cleanly on MIPS (`ctest` transitively depends on ancient `libc` version
which doesn't build on MIPS), but let's save that for another day.

musl has a different aiocb definition; netbsd and OSX have some symbol renaming, and
lwpid_t is signed on freebsd

Musl 1.1.14 defined these incorrectly, and we followed suit. They're
fixed in 1.1.15, so we fix them here as well.

Since these are kernel ABIs, the correct values match other libc
implementations, so we move them up to the topmost module possible.

Following types and function have been added:
* pthread_cond_init
* pthread_condattr_t
* pthread_condattr_init
* pthread_condattr_destroy
* pthread_condattr_setclock [0]
* pthread_condattr_getclock [0][1]

[0] Not available on OSX.
[1] May be unavailable on NetBSD, it is a very recent addition.
    Left out from openbsdlike hierarchy for now.

Copy them into individual platform files instead. Fixes musl build.

Sadly, the sysinfo struct varies slightly between Musl and Glibc / Bionic.

This means that users need to be careful when using the uptime, and should
always cast it to a signed value. Why uptime can be signed is beyond me...

A bunch of definitions were duplicated across, eg, android and linux.
This commit pulls these up to higher levels where they can be shared.

There are many constants defined by langinfo, but we have the
new types, locale_t and nl_item.

We also have several functions, not all of which exist for every
platform:

nl_langinfo
nl_langinfo_l
newlocale
duplocale
freelocale
uselocale
querylocale

Linux-likes have more locale categories than the BSDs (except for
musl). We define the common set of categories at the
src/unix/notbsd/mod.rs level, and leave the rest to the
platform-specific modules.