FreeBSD_HEAD_i386 - Build #3653 - Fixed

FreeBSD_HEAD_i386 - Build #3653 - Fixed:

Build information: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/3653/
Full change log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/3653/changes
Full build log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/3653/console

Change summaries:

303158 by emaste:
libmd: strip local absolute symbols (to link with lld)

Old versions of gas produce an invalid section index. That is ignored by
old versions of ld, but prevents a link with lld.

Submitted by:	Rafael Ávila de Espíndola (earlier version)
Reviewed by:	allanjude
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D6789

303157 by emaste:
libcxxrt: add padding in __cxa_allocate_* to fix alignment

The addition of the referenceCount to __cxa_allocate_exception put the
unwindHeader at offset 0x58 in __cxa_exception, but it requires 16-byte
alignment. In order to avoid changing the current __cxa_exception ABI
(and thus breaking its consumers), add explicit padding in the
allocation routines (and account for it when freeing).

This is intended as a lower-risk change for FreeBSD 11. A "more correct"
fix should be prepared for upstream and -CURRENT.

Reviewed by:	dim
MFC after:	3 days
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D7271

303156 by emaste:
Remove duplicate symbols from libroken version-script.map

Upstream commit r24759 (efed563) prefixed some symbols with rk_, but
introduced 6 duplicate symbols in the version script (because the
rk_-prefixed versions of the symbols were already present).

303155 by kib:
Hide counted_warning(9) under #ifdef _KERNEL braces, to allow building
subr_prf.c in userspace for libsbuf.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week