make iq2000 use constraints.md
        * config/iq2000/i2000.h (REG_CLASS_FROM_LETTER): Delete.
        (CONST_OK_FOR_LETTER_P, CONST_DOUBLE_OK_FOR_LETTER_P): Delete.
        (EXTRA_CONSTRAINT): Delete.
        * config/iq2000/constraints.md: New file.
        * config/iq2000/iq2000.md: Include it.
	(define_insn ""): Delete.
	(movsi_internal2, movhi_internal2, movqi_internal2): Delete
	unsupported constraint letters from patterns.
	(call_value, call_value_internal1): Likewise.
	(call_value_multiple_internal1): Likewise.

From-SVN: r170184