* config/rx-defs.h: Add macros for RX100, RX200, RX600, and
	RX610.
        * config/rx-parse.y: (rx_check_float_support): Add function to
	check floating point operation support for target RX100 and
	RX200.
        * config/tc-rx.c: Add CPU options RX100, RX200, RX600, and RX610.
        * doc/c-rx.texi: Add -mcpu option to recognize macros for RX100,
        RX200, RX600, and RX610