Vscode-cpptools: Expose the inactive lines color setting so it can be set via color scheme

[skelliam]

It's true that Visual Studio does not (I don't think) allow changing this, but Eclipse and others do. Specifically I would like to have a shaded background for inactive preprocessor blocks, like the first image in issue #510. (In fact, this image may have come from Eclipse)

So in the color scheme, could we have a scope like "meta.preprocessor.inactive" or something, that would let users adjust the color to their liking?

Here is an example setting in the color scheme:

Thank you!

[sean-mcmanus]

0.18.0 should have the fix: C_Cpp.inactiveRegionForegroundColor and C_Cpp.inactiveRegionBackgroundColor settings.