non_standard_extension_msbuild_cuda

msbuild.xml

A .vcxproj file containing:

    <CudaCompile Include="foo.notcu" />

results in a failure to build:
    
    nvcc fatal: Don't know what to do with 'C:/path/to/foo.notcu'

because CudaCompile does not pass '-x cu' to nvcc.

While a non-standard extension is not common practice, it is something supported by build system generators like CMake 
(which has a way to mark sources as a specific language regardless of their extension).