constraints.md: New file.

constraints.md: New file.

        * config/alpha/constraints.md: New file.
	* config/alpha/alpha.c: Include tm-constrs.h.
	(alpha_const_ok_for_letter_p, alpha_const_double_ok_for_letter_p,
	alpha_extra_constraint): Remove.
	(alpha_emit_conditional_branch): Use satisfies_constraint_*.
	* config/alpha/alpha-protos.h: Update.
	* config/alpha/alpha.h (REG_CLASS_FROM_LETTER): Remove.
	(CONST_OK_FOR_LETTER_P, CONST_DOUBLE_OK_FOR_LETTER_P): Remove.
	(EXTRA_CONSTRAINT): Remove.
	* config/alpha/alpha.md: Include constraints.md.
	(adddi splitter): Use satisfies_constraint_*.
	* config/alpha/predicates.md (add_operand): Likewise.
	(sext_add_operand, addition_operation): Likewise.

From-SVN: r121847