Bug fixes and tests for nvcc

Bug fixes and tests for nvcc

Feature: Added cuda compiler in separate travis job and implemented
         tests for nvcc.

Feature: Added support for nvcc compiler options --compiler-bindir/-ccbin,
         --output-directory/-odir and --libdevice-directory/-ldir.
         Added tests for these options in test.sh.

Bug fix: Original patch had a statement to avoid using the preprocessed
         input files for nvcc when run_second_cpp is false. Otherwise,
         when a build is necessary and the preprocessed output was used,
         nvcc results with a compiler error. The patch simply ensures
         run_second_cpp is always set to true for the cuda compiler.

Bug fix: The -optf and -odir options are only accepted for nvcc. For other
         compilers, they behave like '-o ptf' resp. '-o dir'.
         A test was added to check this behaviour.