Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Reduce duplication between i386/linux/linux.h and amd64/linux32/linux.h
by moving bits that are MI out into headers in compat/linux.

Reviewed by: Chagin Dmitry dmitry | gmail
MFC after: 2 weeks

linux compat: improve and fix sendmsg/recvmsg compatibility

- implement baseic stubs for capget, capset, prctl PR_GET_KEEPCAPS
and prctl PR_SET_KEEPCAPS.
- add SCM_CREDS support to sendmsg and recvmsg
- modify sendmsg to ignore control messages if not using UNIX
domain sockets

This should allow linux pulse audio daemon and client work on FreeBSD
and interoperate with native counter-parts modulo the differences in
pulseaudio versions.

PR: kern/149168
Submitted by: John Wehle <john@feith.com>
Reviewed by: netchild
MFC after: 2 weeks

Implement a variation of the linux_common_wait() which should
be used by linuxolator itself.

Move linux_wait4() to MD path as it requires native struct
rusage translation to struct l_rusage on linux32/amd64.

MFC after: 1 Month.

Rework r189362, r191883.
The frequency of the statistics clock is given by stathz.
Use stathz if it is available, otherwise use hz.

Pointed out by: bde

Approved by: kib (mentor)

A better fix for handling different FPU initial control words for different
ABIs:
- Store the FPU initial control word in the pcb for each thread.
- When first using the FPU, load the initial control word after restoring
the clean state if it is not the standard control word.
- Provide a correct control word for Linux/i386 binaries under
FreeBSD/amd64.
- Adjust the control word returned for fpugetregs()/npxgetregs() when a
thread hasn't used the FPU yet to reflect the real initial control
word for the current ABI.
- The Linux/i386 ABI for FreeBSD/i386 now properly sets the right control
word instead of trashing whatever the current state of the FPU is.

Reviewed by: bde

Add AT_PLATFORM, AT_HWCAP and AT_CLKTCK auxiliary vector entries which
are used by glibc. This silents the message "2.4+ kernel w/o ELF notes?"
from some programs at start, among them are top and pkill.

Do the assignment of the vector entries in elf_linux_fixup()
as it is done in glibc.

Fix some minor style issues.

Submitted by: Marcin Cieslak <saper at SYSTEM PL>
Approved by: kib (mentor)
MFC after: 1 week

Sanitize arguments to linux_mremap().
Check that only MREMAP_FIXED and MREMAP_MAYMOVE flags are specified.
Check for the page alignment of the addr argument.

Submitted by: rdivacky
MFC after: 1 week

MFp4:
- semi-automatic style fixes
- spelling fixes in comments
- add some comments

MFP4:
Implement prctl().

Submitted by: rdivacky
Tested with: LTP