Implement rand/srand in terms of random/srandom.

Code developed for glibc or older versions of bionic might expect more
randomness than the BSD implementation provides.

Bug: 15829381

(cherry picked from commit 76c241b091b4d9d9a9237d40e814e52ce2917f47)

Change-Id: If721b3f16efdb21cb67df5ec5034c0ba905bd029
4 files changed