* config/crx/crx.md: Make doloop_end pattern usage controllable
	via mloop-nesting=<max-nesting> command line switch. Make sure
	the combiner cannot use doloop_end_<mode> in an illegal way.
	* config/crx/crx.c: Use regs up to r6 for argument passing.
	Refine crx_address_cost (non cst4 displacements are expensive).
	* config/crx/crx.opt: Add switch for mloop-nesting=.

From-SVN: r103518