gdb: Fix alignment computation for structs with only static fields

gdb: Fix alignment computation for structs with only static fields

The current code in gdbtypes.c:type_align incorrectly returns 0 as the
alignment for a structure containing only static fields.  After this
patch the correct value of 1 is returned.  The gdb.base/align.exp test
is extended to cover this case.

gdb/ChangeLog:

	* gdbtypes.c (type_align): A struct with no non-static fields also
	has alignment of 1.

gdb/testsuite/ChangeLog:

	* gdb.base/align.exp: Extend test to cover structures containing
	only static fields.