[arm] Initialize fpu capability bits in arm_active_target

[arm] Initialize fpu capability bits in arm_active_target

Now that we can describe the FPU with the standard ISA bits we need to
initialize them.  However, the FPU settings can be changed with target build
attributes, so we also need to reset them if things change.  This requires
a bit of juggling about with the existing code to ensure that the active
target is reconfigured after each change to the target options.

	* arm-protos.h: Include sbitmap.h
	(arm_configure_build_target): Make public.
	* arm.c (arm_configure_build_target): Now not static.
	(arm_valid_target_attribute_rec): Move internal option check to...
	(arm_valid_target_attribute_tree0: ... here.  Also reconfingure the
	active target.
	(arm_override_options_after_change): Call arm_configure_build_target.
	(isa_all_fpubits): Renamed from isa_fpubits.
	(arm_option_restore): New function.
	(TARGET_OPTION_RESTORE): Register it.
	(arm_configure_build_target): Initialize the FPU capability bits in
	the isa.
	(arm_option_override): Move the code that forces the setting of the
	FPU option before the call to arm_configure_build_target.
	* arm.opt (march): Mark as Save.
	(mcpu, mtune): Likewise.
	* arm-c.c (arm_pragma_target_parse): Reconfigure the build target
	after pragmas change the target options.

From-SVN: r243710