Add a hack for Travis so that llvm-gcc can build native executables.
This could be useful if KLEE tests want to use the bitcode compiler
as a native compiler.
Added tests to for _testingUtils.c (currently failing due to a bug in printing 64bit numbers)
Fixing this bug will expose a failing test case for Concrete/ConstantExpr.ll
Fixed Concrete/ConstanstExpr.ll

The difference between a 64bit pointer truncated to 32 bits and the
original 64bit pointer would never be 0 if any of the high 32bits in
the pointer were test. Due to the 64bit printing buf in _testingUtils
this was not exposed before.

The fix clears the top 32bits of the difference.
Fix the bug in printing 64bit numbers, set to test to expect passing