For PR418:

For PR418:
Add an example program that utilizes multiple threads in the JIT to process
work. This was used by Evan Jones as the original test case for ensuring
that the ExecutionEngine was thread safe.

Original source by Evan Jones (adapted from other LLVM JIT examples) and
made LLVM style compliant by Reid Spencer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22411 91177308-0d34-0410-b5e6-96231b3b80d8