llvm-gcc4: Enable various optimizations at -O1/-O2

Hi All,

I have installed llvm-gcc4 patch to enable various llvm optimizations at -O1/-O2/-O3.

This means instead of

$ llvm-gcc4 --emit-llvm foo.c -o foo.bc
$ opt foo.bc -o foo_optimized.bc
$ llc foo_optimized.bc -o foo.o

One can directly use

$ llvm-gcc4 -O2 foo.c -o foo.o

to get optimized foo.o