Add script to run VecCore tests
This is the script I usually run before pushing a branch. It tests compilation and runs tests with GCC-4.9.3, GCC-5.3.0, ICC, and Clang (this is on Linux).
For CUDA, all these compilers currently just work as the host compiler.
I would like this to be merged so that others can modify it to their setups and run this too before pushing.