Add fast interrupt.

Add fast interrupt.

	*  config/microblaze/microblaze-protos.h: Rename
	microblaze_is_interrupt_handler to microblaze_is_interrupt_variant.
	*  config/microblaze/microblaze.c (microblaze_attribute_table): Add
	fast_interrupt.
	(microblaze_fast_interrupt_function_p): New function.
	(microblaze_is_interrupt_handler): Rename to
	microblaze_is_interrupt_variant and add fast_interrupt check.
	(microblaze_must_save_register): Use microblaze_is_interrupt_variant.
	(save_restore_insns): Likewise.
	(compute_frame_size): Likewise.
	(microblaze_function_prologue): Add FAST_INTERRUPT_NAME.
	(microblaze_globalize_label): Likewise.
	*  config/microblaze/microblaze.h: Define FAST_INTERRUPT_NAME.
	*  config/microblaze/microblaze.md: Use wrapper
	microblaze_is_interrupt_variant.

From-SVN: r196474