Proper support for natvis files in addons

Hi!

I am using an addon that comes with a Visual Studio C++ debugger visualization file (natvis) in their src/ folder, and it's a bit of a pain because everytime I regenerate the project solution, it seems the OF generator treats it as a "C/C++ compiler" item, which means the C++ compiler is trying to compile the natvis and fails.

The fix should be simple, the OF generator should recognize natvis files and flag them as "C++ debugger visualization file" during the vcxproj generation step.

However, I have no idea how the generator works or where that fix would make sense. If someone can point me to it, or implement it, it would be a great time saver.

Thanks!

Start by locating the openFrameworks generator code responsible for vcxproj generation and inspect how files in an addon src/ folder are classified. Reproduce the project regeneration with a .natvis file, then verify that it is emitted as a C++ debugger visualization file rather than a C/C++ compiler item and no longer sent to the compiler.