Add FreeBSD/mips architecture.

Add FreeBSD/mips architecture.

This has been tested for the n64 and o32 ABIs.  Signal frame unwinders for
both ABIs are provided.  FreeBSD/mips requires custom linkmap offsets since
it contains an additional l_off member in 'struct link_map' that other
FreeBSD platforms do not have.  Support for collecting and supplying
general purpose and floating point register sets are provided.  Common
routines for working with native format register sets are exported for
use by the native target.

gdb/ChangeLog:

	* Makefile.in (ALL_TARGET_OBS): Add mips-fbsd-tdep.o.
	(ALLDEPFILES): Add mips-fbsd-tdep.c.
	* NEWS: Mention new FreeBSD/mips target.
	* configure.tgt: Add mips*-*-freebsd*.
	* mips-fbsd-tdep.c: New file.
	* mips-fbsd-tdep.h: New file.

gdb/doc/ChangeLog:

	* gdb.texinfo (Contributors): Add SRI International and University
	of Cambridge for FreeBSD/mips.