MFC r287292:
Switch libc from using _sig{procmask,action,suspend} symbols, which
are aliases for the syscall stubs and are plt-interposed, to the
libc-private aliases of internally interposed sigprocmask() etc.

MFC r287300:
Use libthr interposed functions instead of syscalls, in posix_spawn()'
child.

MFC r279084,280713: setmode(): Use sysctl kern.proc.umask instead of umask()
if possible.

The kern.proc.umask.<pid> sysctl allows querying the umask without
temporarily modifying it.

r280713 is the actual change, while r279084 is a whitespace change.

MFC r279186:
setmode(3): Make sure that setmode sets errno on failure.

Our man page already documented this partially but now
we provide more consistent behavior.

PR: 136669
Obtained from: NetBSD (CVS rev. 1.31, 1.33)
Relnotes: yes

MFC r287292:
Switch libc from using _sig{procmask,action,suspend} symbols, which
are aliases for the syscall stubs and are plt-interposed, to the
libc-private aliases of internally interposed sigprocmask() etc.

MFC r287300:
Use libthr interposed functions instead of syscalls, in posix_spawn()'
child.

MFC r279084,280713: setmode(): Use sysctl kern.proc.umask instead of umask()
if possible.

The kern.proc.umask.<pid> sysctl allows querying the umask without
temporarily modifying it.

r280713 is the actual change, while r279084 is a whitespace change.

MFC r279186:
setmode(3): Make sure that setmode sets errno on failure.

Our man page already documented this partially but now
we provide more consistent behavior.

PR: 136669
Obtained from: NetBSD (CVS rev. 1.31, 1.33)
Relnotes: yes