Problem reported by Bruce Korb in:
https://lists.gnu.org/r/bug-gnulib/2018-06/msg00030.html
I reproduced the crash on 32-bit sparc with Oracle Studio 12.6
with 'cc -O2 -xmemalign=8s'.
* lib/random_r.c: Include string.h, for memcpy.
(get_int32, set_int32): New functions.
(__srandom_r, __initstate_r, __setstate_r, __random_r):
Use them to avoid assumption that state pointer is aligned.
(__random_r): Avoid integer overflow if INT_MAX == UINT32_MAX.
* tests/test-random_r.c (test_failed): New function.
(main): Use it, to test for alignment bugs.