MFC r272823:

Move the SCTP syscalls to netinet with the rest of the SCTP code. The
syscalls themselves are tightly coupled with the network stack and
therefore should not be in the generic socket code.

The following four syscalls have been marked as NOSTD so they can be
dynamically registered in sctp_syscalls_init() function:
sys_sctp_peeloff
sys_sctp_generic_sendmsg
sys_sctp_generic_sendmsg_iov
sys_sctp_generic_recvmsg

The syscalls are also set up to be dynamically registered when COMPAT32
option is configured.

As a side effect of moving the SCTP syscalls, getsock_cap needs to be
made available outside of the uipc_syscalls.c source file. A proper
prototype has been added to the sys/socketvar.h header file.

API tests from the SCTP reference implementation have been run to ensure
compatibility. (http://code.google.com/p/sctp-refimpl/source/checkout)

MFC r317845-r317846

r317845:
Provide a freebsd32 implementation of sigqueue()

The previous misuse of sys_sigqueue() was sending random register or
stack garbage to 64-bit targets. The freebsd32 implementation preserves
the sival_int member of value when signaling a 64-bit process.

Document the mixed ABI implementation of union sigval and the
incompability of sival_ptr with pointer integrity schemes.

Reviewed by: kib, wblock
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D10605

r317846:
Regen post r317845.

MFC with: r317845
Sponsored by: DARPA, AFRL

MFC r277610 (by jillies):

Add futimens and utimensat system calls.

MFC r276564, r276654:

Cast *path to silence clang -Wpointer-sign warning.

Indeed, instead of hiding the kern___getcwd() bug by bogus cast
in r276564, change path type to char * (pathnames are always char *).
And remove bogus casts of malloc().
kern___getcwd() internally doesn't actually use or support u_char *
paths, except to copy them to a normal char * path.

These changes are not visible to libc as libc/gen/getcwd.c misdeclares
__getcwd() as taking a plain char * path.

While here remove _SYS_SYSPROTO_H_ for __getcwd() syscall as
we always have sysproto.h.

MFC r274462: Add the ppoll() system call.

MFC r270691:
Fix handling of the third argument for fcntl(2). The native syscall
uses long for arg, which needs translation.

MFC r276564, r276654:

Cast *path to silence clang -Wpointer-sign warning.

Indeed, instead of hiding the kern___getcwd() bug by bogus cast
in r276564, change path type to char * (pathnames are always char *).
And remove bogus casts of malloc().
kern___getcwd() internally doesn't actually use or support u_char *
paths, except to copy them to a normal char * path.

These changes are not visible to libc as libc/gen/getcwd.c misdeclares
__getcwd() as taking a plain char * path.

While here remove _SYS_SYSPROTO_H_ for __getcwd() syscall as
we always have sysproto.h.

MFC r274462: Add the ppoll() system call.

MFC r270691:
Fix handling of the third argument for fcntl(2). The native syscall
uses long for arg, which needs translation.