Add ability for GAS input to set section alignment in the same way GAS does:

Add ability for GAS input to set section alignment in the same way GAS does:
if the first thing in the section is a .align, that specifies the section
alignment.

* objfmt.h (yasm_objfmt_module): Add section_align() function.
(yasm_objfmt_section_align): Add wrapper for module section_align().
* xdf-objfmt.c, elf-objfmt.c, bin-objfmt.c, dbg-objfmt.c, coff-objfmt.c:
Implement.

* gas-bison.y (gas_parser_align): Call new yasm_objfmt_section_align() rather
than creating an align bytecode if .align is the first bytecode in the
section.

* gassectalign.asm: New test for this.

svn path=/trunk/yasm/; revision=1315