make fr30 use constraints.md
	* config/fr30/constraints.md: New file.
	* config/fr30/fr30.md: Include it.
	* config/fr30/fr30.h (REG_CLASS_FROM_LETTER): Delete.
	(CONST_OK_FOR_LETTER_P, CONST_DOUBLE_OK_FOR_LETTER_P): Delete.
	(EXTRA_CONSTRAINT): Delete.

From-SVN: r170172