Add some comments. Cleanup formatting.

Add some comments.  Cleanup formatting.

(type attribute): Add pstore and call.
(return define_delay): Reorganize to make clearer.
(call/sfunc define_delay): Define.
(cbranch define_delay): Define to have annul-true delay slot.
(subsi3): Use arith_reg_operand for operand 2.
(shift patterns): Use const_int_operand instead of immediate_operand
for shift counts.
(push): Add pstore constraint case.
(movsi_i): Move t/z constraint pair to the front of the list.
(calli, call_valuei): Add "call" attribute.

From-SVN: r9888