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.

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

Also move them to the common Linux module, as they are not platform-specific.
See include/uapi/linux/falloc.h.

It needs to be skipped during testing because there's no way to include
a combination of headers that will expose it without giving a "type has
already been defined" error.

We need to create an initialized sigaction struct for Linux syscalls
thus its fields need to be public.

The field was named _restorer before but system libc/kernel uapi name the field
sa_restorer.

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.

Add netlink constants from linux/netlink.h

Signed-off-by: Jana Radhakrishnan <mrjana@gmail.com>