Fix Thumb-2 BL detection

Fix Thumb-2 BL detection

2016-07-01  Thomas Preud'homme  <thomas.preudhomme@arm.com>

bfd/
	* elf32-arm.c (using_thumb2_bl): New function.
	(arm_type_of_stub): Declare thumb2 variable together and change type
	to bfd_boolean.  Use using_thumb2_bl () to determine whether
	THM_MAX_FWD_BRANCH_OFFSET or THM2_MAX_FWD_BRANCH_OFFSET should be
	checked for BL range.
	(elf32_arm_final_link_relocate): Use using_thumb2_bl () to determine
	the bit size of BL offset.

ld/
	* testsuite/ld-arm/arm-elf.exp (Thumb-2 BL): Assemble for ARMv7.
	(Thumb-2 BL on ARMv6-M): New testcase.
	* testsuite/ld-arm/thumb2-bl.d: Do not try to match testcase filename.
	* testsuite/ld-arm/thumb2-bl.s: Do not select architecture.