MFC r279307:

MFC r279307:

Make libcxxrt's parsing of DWARF exception handling tables work on
architectures with strict alignment, by using memcpy() instead of
directly reading fields.

Reported by:	Daisuke Aoyama <aoyama@peach.ne.jp>
Reviewed by:	imp, bapt
Tested by:	bapt
Differential Revision: https://reviews.freebsd.org/D1967

MFC r279310:

Since newer versions of compiler-rt require unwind.h, and we want to use
the copy in libcxxrt for it, fix the arm-specific header to define the
_Unwind_Action type.

Submitted by:	andrew

git-svn-id: svn://svn.freebsd.org/base/stable/10@279456 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f