Add rudimentary support for atomics on RX.  It is implemented by flipping
interrupts off/on around the atomic sequences.

gcc/
	* config/rx/rx-protos.h (is_interrupt_func, is_fast_interrupt_func):
	Forward declare.
	(rx_atomic_sequence): New class.
	* config/rx/rx.c (rx_print_operand): Use symbolic names for PSW bits.
	(is_interrupt_func, is_fast_interrupt_func): Make non-static and
	non-inline.
	(rx_atomic_sequence::rx_atomic_sequence,
	rx_atomic_sequence::~rx_atomic_sequence): New functions.
	* config/rx/rx.md (CTRLREG_PSW, CTRLREG_USP, CTRLREG_FPSW, CTRLREG_CPEN,
	CTRLREG_BPSW, CTRLREG_BPC, CTRLREG_ISP, CTRLREG_FINTV,
	CTRLREG_INTB): New constants.
	(FETCHOP): New code iterator.
	(fethcop_name, fetchop_name2): New iterator code attributes.
	(QIHI): New mode iterator.
	(atomic_exchange<mode>, atomic_exchangesi, xchg_mem<mode>,
	atomic_fetch_<fetchop_name>si, atomic_fetch_nandsi,
	atomic_<fetchop_name>_fetchsi, atomic_nand_fetchsi): New patterns.

From-SVN: r236075