Adding nbench to the llvm test-suite

As per [1] I am going to add [2] to the llvm test-suite. I hope nobody is currently working on that area (if anybody is working please do let me know)

Rajika

[1] - http://llvm.org/OpenProjects.html#llvmtest
[2] - http://www.tux.org/~mayer/linux/bmark.html