Move extern variable definitions to the header file.

Approved by:	kib (mentor)

r189861:
Include linux_futex.h before linux_emul.h

r189862:
Ignore FUTEX_FD op, as it is done by linux.

r189867:
Sort include files in the alphabetical order.

Approved by:	kib (mentor)

r178976 (rdivacky):
Implement robust futexes. Most of the code is modelled after
what Linux does. This is because robust futexes are mostly
userspace thing which we cannot alter. Two syscalls maintain
pointer to userspace list and when process exits a routine
walks this list waking up processes sleeping on futexes
from that list.

r183871:
Make robust futexes work on linux32/amd64. Use PTRIN to read
user-mode pointers. Change types used in the structures definitions to
properly-sized architecture-specific types.

r185002:
In the robust futexes list head, futex_offset shall be signed,
and glibc actually supplies negative offsets. Change l_ulong to l_long.

Approved by:	kib (mentor)

MFC rev. 1.3 of sys/compat/linux/linux_futex.h:

	o	Add stub support for some new futex operations,
		so the annoying message is not printed.

	o	Don't warn about FUTEX_FD not being implemented
		and return ENOSYS instead of 0 (eg. success).

	o	Clear FUTEX_PRIVATE_FLAG as we actually implement
		only private futexes so there is no reason to
		return ENOSYS when app asks for a private futex.
		We don't reject shared futexes because they worked
		just fine with our implementation so far.

Approved by:	kib (mentor)
Tested by:	bsam

	semi-automatic style(9)

The futex stuff already differs a lot (only a small part does not differ)
from NetBSD, so we are already way off and can't apply changes from NetBSD
automatically. As we need to merge everything by hand already, we can even
make the files comply to our world order.

Please don't style(9) the NetBSD code, we want to stay in sync. Not imported
on a vendor branch since we need local changes.

Sponsored by:	Google SoC 2006
Submitted by:	rdivacky
With help from:	manu@NetBSD.org
Obtained from:	NetBSD (linux_{futex,time}.*)