Update cmVisualStudio10TargetGenerator.cxx

In our work we are using cmake to generate c++/cli projects where we use mixed code (managed and unmanaged).
Setting the <CLRSupport> true for the project - based on if an resx-file is pressent - prevents us from using native cpp code.
Also this do not address that some projects will need to set other options like clr:pure, clr:safe.
This could be implemented as a cmake option, so it is possible to specify exactly what is needed.