Add .refsym to msp430 backend

* config/tc-msp430.c (msp430_refsym): New: ".refsym <symbol>"
* doc/c-msp430.texi (MSP430 Directives): Document it.

The purpose of this patch is to provide a way for one object file
to require the inclusion of another object, without having to
allocate space for a .word address reference.
	New gdbserver option --debug-format=timestamp.
	* NEWS: Mention it.

	gdbserver/
	* configure.ac (AC_CHECK_FUNCS): Add test for gettimeofday.
	* configure: Regenerate.
	* config.in: Regenerate.
	* Makefile.in (SFILES): Add debug.c.
	(OBS): Add debug.o.
	* debug.c: New file.
	* debug.h: New file.
	* linux-aarch64-low.c (*): Update all debugging printfs to use
	debug_printf instead of fprintf.
	* linux-arm-low.c (*): Ditto.
	* linux-cris-low.c (*): Ditto.
	* linux-crisv32-low.c (*): Ditto.
	* linux-m32r-low.c (*): Ditto.
	* linux-sparc-low.c (*): Ditto.
	* linux-x86.c (*): Ditto.
	* linux-low.c (*): Ditto.
	(linux_wait_1): Add calls to debug_enter, debug_exit.
	(linux_wait): Remove redundant debugging printf.
	(stop_all_lwps): Add calls to debug_enter, debug_exit.
	(linux_resume, unstop_all_lwps): Ditto.
	* mem-break.c (*): Update all debugging printfs to use
	debug_printf instead of fprintf.
	* remote-utils.c (*): Ditto.
	* thread-db.c (*): Ditto.
	* server.c #include <ctype.h>, "gdb_vecs.h".
	(debug_threads): Moved to debug.c.
	(*): Update all debugging printfs to use debug_printf instead of
	fprintf.
	(start_inferior): Replace call to fflush with call to debug_flush.
	(monitor_show_help): Mention set debug-format.
	(parse_debug_format_options): New function.
	(handle_monitor_command): Handle "monitor set debug-format".
	(gdbserver_usage): Mention --debug-format.
	(main): Parse --debug-format.
	* server.h (debug_threads): Declaration moved to debug.h.
	#include "debug.h".
	* tracepoint.c (trace_debug_1) [!IN_PROCESS_AGENT]: Add version of
	trace_debug_1 that uses debug_printf.
	(tracepoint_look_up_symbols): Update all debugging printfs to use
	debug_printf instead of fprintf.

	doc/
	* gdb.texinfo (Server): Mention --debug-format=all|none|timestamp.
	(gdbserver man): Ditto.

	testsuite/
	* gdb.server/server-mon.exp: Add tests for "set debug-format".
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