This is part of an overall effort to use the name, "WinRT", rather than "WindowsRT" (or "Windows RT"), as the shorthand name often seems to mean something different than the longhand name. (WinRT is an API, Windows RT is a product name)
This change removes some code that attempted to allow non-standard window sizes, the idea of which was to do display scaling, and a hackish one at that. If display scaling is needed, use SDL_Renderer as appropriate.
- moved SDL_WinRTApp.* from src/video/windowsrt/ to src/core/winrt/, and renamed them to SDL_winrtapp.* (to mimick case-sensitivity used elsewhere in SDL)
- renamed all "windowsrt" directories (in src) to "winrt", as the shorthand name is used more often (and, IMO, "WinRT" != "Windows RT", not entirely at least)
