[binutils-gdb] Remove rust_type_alignment

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 2fff16dd8c25831fb5fbf198ca86d5befff629be ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: 2fff16dd8c25831fb5fbf198ca86d5befff629be

Remove rust_type_alignment

rust_type_alignment is not needed now that gdb has type alignment
code.  So, this removes it.

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

	* rust-lang.c (rust_type_alignment): Remove.
	(rust_composite_type): Use type_align.