Always initialize PRNG using random data from the OS.

libgfortran:

2016-08-16  Janne Blomqvist  <jb@gcc.gnu.org>

        * intrinsics/random.c (master_init): New variable.
        (init_rand_state): Move below getosrandom (), maybe initialize
        master_state.
        (random_seed_i4): If called with no arguments, set master_init to
        false, and reinitialize. If called with PUT=, set master_init to
        true.
        (random_seed_i8): Likewise.

testsuite:

2016-08-16  Janne Blomqvist  <jb@gcc.gnu.org>

        * gfortran.dg/random_4.f90: Initialize seed before using, handle
        the last special seed value.
        * gfortran.dg/random_7.f90: Use size for last array member instead
        of hardcoded value.

From-SVN: r239611