Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r244236,r244408,r244915,r247054,r251512:

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 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.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Source changes to allow building a cross-debugger. Move solib.c and
solib-svr4.c to the MD makefiles because they are native files for
alpha and sparc64, but target files for amd64, i386 and ia64.

Note that kgdb(1) does not yet build as a cross-debugger due to
libkvm.

Update config.h to account for the prgregset_t and psaddr_t types
that have been added to <sys/procfs.h>. This change has no effect
because the source file that would be affected is not compiled on
FreeBSD. Hence, this is for completeness only.

Add bmake glue for gdb 6.1.1. Supports alpha, amd64, i386, ia64
and sparc64.

Note that the debugger doesn't support threading, nor kernel
debugging yet.