a test for when the clang compiler method signature mismatches with the julia ccall one

The clang / llvm-gcc compiler that ships with Apple does not cast 8 bit values to the appropriate size in function arguments. I worked around this bug in the fall to correct boxing of 8 bit values and get the code to compile, but I realized this could affect ccall also (if the target code was compiled with llvm-gcc / clang) so I started to put together this testsuite for ccall to demonstrate the error.