gas object file locations

With the update to newer autotools, some gas object files are now
built in config/, breaking xtensa-elf and ia64-vms.  This patch fixes
the dependencies.

	* configure.ac: Specify extra_objects with leading "config/"
	for xtensa-relax.o and te-vms.o.  Use case statements to unique
	extra_objects.  Formatting.
	* configure: Regenerate.

(cherry picked from commit e11078da)