Both shiboken extension and executable have same name on windows

Both shiboken2/shibokenmodule/CMakeLists.txt
and shiboken2/generator/CMakeLists.txt specify a target name of "shiboken".
This means that the .pdb files generated for them will have the same name, and thus override each other when copied to the final package.

On Unix systems the extension name usually has an additional suffix, thus causing no conflicts.

We should find a way (possibly add some suffix) to make sure that .pdb files don't get overridden.