[arm] Add new isa quirk bit for Cortex-M3 ldrd issue.

[arm] Add new isa quirk bit for Cortex-M3 ldrd issue.

With the new data structures it is trivial to add a new field and we
aren't (too) limited as to the number we have.  This patch adds a new
bit to describe the need for a particular compiler behaviour
modification: in this case a quirk in the cortex-m3.

	* arm-isa.h (enum isa_feature): Add isa_quirk_cm3_ldrd.
	(ISA_ALL_QUIRKS): New macro.
	* arm-cores.def (cortex-m3): Add isa_quirk_cm3_ldrd to isa feature list.
	* arm.c (isa_quirkbits): New feature-list bitmap.
	(arm_configure_build_target): Ignore quirk bits when comparing an
	architecture feature list with a CPU feature list.
	(arm_option_override): Initialize_isa_quirkbits.  If the user has
	not specified -m[no-]fix-cortex-m3-ldrd, automatically enable the
	feature if isa_quirk_cm3_ldrd appears in the isa feature list.

From-SVN: r243701