python: Implement btrace Python bindings for record history.

python: Implement btrace Python bindings for record history.

This patch implements the gdb.Record Python object methods and fields for
record target btrace.  Also, implement a stub for record target full.

Signed-off-by: Tim Wiederhake <tim.wiederhake@intel.com>
gdb/ChangeLog:

	* Makefile.in (SUBDIR_PYTHON_OBS): Add py-record-btrace.o,
	py-record-full.o.
	(SUBDIR_PYTHON_SRCS): Add py-record-btrace.c, py-record-full.c.
	* python/py-record-btrace.c, python/py-record-btrace.h,
	python/py-record-full.c, python/py-record-full.h: New file.
	* python/py-record.c: Add include for py-record-btrace.h and
	py-record-full.h.
	(recpy_method, recpy_format, recpy_goto, recpy_replay_position,
	recpy_instruction_history, recpy_function_call_history, recpy_begin,
	recpy_end): Use functions from py-record-btrace.c and py-record-full.c.
	* python/python-internal.h (PyInt_FromSsize_t, PyInt_AsSsize_t):
	New definition.
	(gdbpy_initialize_btrace): New export.
	* python/python.c (_initialize_python): Add gdbpy_initialize_btrace.

Change-Id: I8bd893672ffc7e619cc1386767897249e125973a