Expose type alignment on gdb.Type

Expose type alignment on gdb.Type

This adds an "alignof" attribute to gdb.Type in the Python API.

2018-04-30  Tom Tromey  <tom@tromey.com>

	* NEWS: Mention Type.align.
	* python/py-type.c (typy_get_alignof): New function.
	(type_object_getset): Add "alignof".

2018-04-30  Tom Tromey  <tom@tromey.com>

	* python.texi (Types In Python): Document Type.align.

2018-04-30  Tom Tromey  <tom@tromey.com>

	* gdb.python/py-type.exp: Check align attribute.
	* gdb.python/py-type.c: New "aligncheck" global.