Was able to move some of them up one level so they are valid on more
platforms with less duplication

These aren't exposed on non-MIPS musl targets, but since they're
part of a kernel API, they're still applicable, so we just don't
test them there but expose them anyways.

Note that termios2 doesn't exist on powerpc(64), termios
is used instead.

Signed-off-by: Tom Kirchner <tjk@amazon.com>
Signed-off-by: Ben Cressey <bcressey@amazon.com>

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.