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.
