Add simple RNG to avoid library differences

Now the reference output is specific to the local implementation, avoiding
dependencies on the library that could change from release to release on
the same architectures.

Tested on x86_64 and ARMv7 (32-bits), so should work on any 32-bit and
64-bit architectures. It's also probably safe on 16-bit archs.


git-svn-id: https://llvm.org/svn/llvm-project/test-suite/trunk@177148 91177308-0d34-0410-b5e6-96231b3b80d8