pdp11-protos.md (arith_operand, [...]): Delete

pdp11-protos.md (arith_operand, [...]): Delete

* config/pdp11/pdp11-protos.md (arith_operand,
const_immediate_operand, expand_shift_operand,
immediate15_operand): Delete
* config/pdp11/pdp11.c: Ditto.
* config/pdp11/pdp11.h (REG_CLASS_FROM_LETTER,
CONST_OK_FOR_LETTER_P, CONST_DOUBLE_OK_FOR_LETTER_P,
EXTRA_CONSTRAINT): Delete.
* config/pdp11/pdp11.md (various): Use standard constraints
instead of removed ones.
* config/pdp11/constraints.md: New file.
* config/pdp11/predicates.md: New file.

From-SVN: r165784