Replace KISS PRNG with xorshift1024* using per-thread state.

frontend:

2016-08-11  Janne Blomqvist  <jb@gcc.gnu.org>

	* check.c (gfc_check_random_seed): Use new seed size in check.
	* intrinsic.texi (RANDOM_NUMBER): Updated documentation.
	(RANDOM_SEED): Likewise.


testsuite:

2016-08-11  Janne Blomqvist  <jb@gcc.gnu.org>

	* gfortran.dg/random_7.f90: Take into account that the last seed
	value is the special p value.
	* gfortran.dg/random_seed_1.f90: Seed size is now constant.


libgfortran:
2016-08-11  Janne Blomqvist  <jb@gcc.gnu.org>

	* intrinsics/random.c: Replace KISS with xorshift1024* using
	per-thread state.
	* runtime/main.c (init): Don't call random_seed_i4.

From-SVN: r239356