Don't use PyLong_FromLong

This changes gdb to avoid PyLong_FromLong, preferring to
gdb_py_object_from_longest instead.

gdb/ChangeLog
2020-09-15  Tom Tromey  <tromey@adacore.com>

	* python/python.c (gdbpy_parameter_value): Use
	gdb_py_object_from_longest.
	* python/py-type.c (convert_field, typy_range): Use
	gdb_py_object_from_longest.
	* python/py-tui.c (gdbpy_tui_width, gdbpy_tui_height): Use
	gdb_py_object_from_longest.
	* python/py-lazy-string.c (stpy_get_length): Use
	gdb_py_object_from_longest.
	* python/py-infthread.c (thpy_get_num, thpy_get_global_num): Use
	gdb_py_object_from_longest.
	* python/py-infevents.c (create_memory_changed_event_object): Use
	gdb_py_object_from_longest.
	* python/py-inferior.c (infpy_get_num): Use
	gdb_py_object_from_longest.
	(infpy_get_pid): Likewise.