[NDS32] Add unaligned access support.

[NDS32] Add unaligned access support.

gcc/
	* config/nds32/constants.md (unspec_volatile_element): Add enum values
	for unaligned access.
	* config/nds32/nds32-intrinsic.c: Implementation of expanding
	unaligned access.
	* config/nds32/nds32-intrinsic.md: Likewise.
	* config/nds32/nds32_intrinsic.h: Likewise.
	* config/nds32/nds32.h (nds32_builtins): Likewise.
	* config/nds32/nds32.opt (munaligned-access): New option.
	* config/nds32/nds32.c (nds32_asm_file_start): Display
	flag_unaligned_access status.

Co-Authored-By: Chung-Ju Wu <jasonwucj@gmail.com>
From-SVN: r259545