Add optimized implementation of mersenne twister for aarch64

Add optimized implementation of mersenne twister for aarch64

2017-07-23  Michael Collison  <michael.collison@arm.com>

	Add optimized implementation of mersenne twister for aarch64
	* config/cpu/aarch64/opt/ext/opt_random.h: New file.
	(__arch64_recursion): New function.
	(__aarch64_lsr_128): New function.
	(__aarch64_lsl_128): New function.
	(operator==): New function.
	(simd_fast_mersenne_twister_engine): Implement
	method _M_gen_rand.
	* config/cpu/aarch64/opt/bits/opt_random.h: New file.
	* include/ext/random: (simd_fast_mersenne_twister_engine):
	add _M_state private array.

From-SVN: r250464