(storehi_bigend): New expansion pattern.

(storeinthi): Rework to generate better code, add big-endian support.
(movhi): Add support for processors running in big-endian mode.
(movhi_bigend): New expansion pattern.
(matcher for movhi): Remove incorrect alternative for storing HImode to
memory.  Only match when little endian.
(matcher for big-endian movhi): New pattern.
(matchers/peepholes for extended pre/post increment HImode loads): Only
match when little-endian.
(matcher for operating on adjacent memory locations): Load operation into
arith operands.
(peepholes for extended pre-increment byte loads): New patterns.

From-SVN: r7448