sigaltstack(2): Bring it closer to POSIX.

POSIX says that sigaltstack() shall return EINVAL if the "ss argument
is not a null pointer, and the ss_flags member pointed to by ss contains
flags other than SS_DISABLE".
Merge branch 'master' into gsocdrm_jfree
mpt(4): Use cam_calc_geometry() directly.
bce.4: Remove unnecessary .Pp and trailing whitespace.
mpt.4: Uncomment reference to mps(4).
Merge branch 'master' into gsocdrm_jfree
<iso646.h>: Avoid conflicts w/ C++ keywords.

Fix whitespace too.

Obtained-from:   FreeBSD
Bring in FreeBSD's msun code for our libm.

Our current libm is a mix of NetBSD and FreeBSD.  To ease
maintainability, sync with FreeBSD as requested by John Marino.

Obtained-from:   FreeBSD
Add <tgmath.h>.

Obtained-from:   FreeBSD
Stop overwriting /etc/services.

Users should be able to configure their services database, so those
changes shouldn't be blown away when they do a make upgrade.

Dragonfly-bug: <http://bugs.dragonflybsd.org/issues/2564>
Bump library versions for libc and libm.

I forgot to do this for the libm changes, and it's required since some
of the symbols moved around.
Merge branch 'master' into gsocdrm_github