Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add a new knob WITH_DEBUG_FILES to control the building of standalone
debug files for userland programs and libraries. The "-g" debug flag
is automatically applied when WITH_DEBUG_FILES is set.

The debug files are now named ${prog}.debug and ${shlib}.debug for
consistency with other systems and documentation. In addition they are
installed under /usr/lib/debug, to simplify the process of installing
them if needed after a crash. Users of bsd.{prog,lib}.mk outside of the
base system place the standalone debug files in a .debug subdirectory.
GDB automatically searches both of these directories for standalone
debug files.

Thanks to everyone who contributed changes, review, and testing during
development.

Do not include <sys/ptrace.h> if we're building a cross-debugger, ptrace isn't
used anyway, and it breaks the build, since sys/ptrace.h now includes
<machine/reg.h>

Approved by: re

Fix typo in comment

Unbreak the arm build, by spelling LIBSRCS correctly.

Do not build fbsd-threads.c if we're building a cross-debugger.

MFC after: 3 days

Add thread support for arm.

MFC After: 1 week

There's no reason why we couldn't attach to a live process on arm.

MFC After: 1 week

Architecture specific portions of gdb for arm.

Submitted by: cognet@