Needless enabling of languages when not building example programs

[eyalroz]

The library is intended for use with C++ and/or CUDA compilers; but - we don't need those to build anything, unless we're building example programs. Thus there is no reason for CMake to check for the presence of a compiler, especially not a CUDA compiler, just to "build" the package and install it.

So, let's drop the LANGUAGES argument of the project() command invocation.