Add a new class gdb.Architecture which exposes GDB's

	Add a new class gdb.Architecture which exposes GDB's
	internal representation of architecture via GDB Python API.

	* Makefile.in: Add entries corresponding to the new file
	python/py-arch.c.
	* NEWS (Python Scripting): Add entries for the new class
	gdb.Architecture and the new method gdb.Frame.architecture.
	* python/py-arch.c: Implement gdb.Architecture class.
	* python/py-frame.c (frapy_arch): Implement the method
	gdb.Frame.architecture().
	(frame_object_methods): Add 'architecture' to the method table.
	* python/python-internal.h: Add declarations of new utility
	functions.
	* python/python.c (_initialize_python): Initialize
	gdb.Architecture class.

	* doc/gdb.texinfo (Architectures In Python): New sub-sub-section
	describing the gdb.Architecture class.
	(Frames In Python): Add description about the new method
	gdb.Frame.architecture().

	* testsuite/gdb.python/frame.exp: Add a test for
	gdb.Frame.architecture() method.