[arm] Permit 'auto' in -mfpu

[arm] Permit 'auto' in -mfpu

Now we finally have the infrastructure in place we can now derive
details of the FPU from a CPU entry.  This patch enables this for the
existing cores that already have an explicit FPU in their product names.

	* arm-fpus.def: Add CNAME field to all FPU definitions.
	* genopt.sh: Use explicit enumeration tags for FPU entries.
	* arm-tables.opt: Regenerated.
	* arm.opt (mfpu): Provide initial value.
	* arm-opts.h (enum fpu_type): Build the enumeration from the list of
	available FPUs.  Add 'auto' entry on the end.
	* arm.c (arm_configure_build_target): Only do explicit configuration
	of the FPU features if the selected FPU is not 'auto'.
	(arm_option_override): Adjust initialization of arm_fpu_index.
	Emit an error if we have a hard float ABI request, but the processor
	does not support floating-point.
	(arm_option_print): Handle -mfpu=auto.
	(arm_valid_target_attribute_rec): Don't permit fpu=auto in pragmas
	or function attributes.
	(arm_identify_fpu_from_isa): Handle effective soft-float when
	the FPU is automatically detected.
	* arm-cores.def (arm1136jf-s): Add feature ISA_FP_DBL.
	(arm1176jzf-s): Likewise.
	(mpcore): Likewise.
	(arm1156t2f-s): Likewise.

From-SVN: r243716