Fixed compiling Windows RT code on Visual Studio 2013

--HG--
rename : src/render/direct3d11/SDL_render_d3d11_winrthelpers.cpp => src/render/direct3d11/SDL_render_winrt.cpp
rename : src/render/direct3d11/SDL_render_d3d11_winrthelpers_cpp.h => src/render/direct3d11/SDL_render_winrt.h
Updated framework version to match dylib version.
Actually the dylib compatibility version is 3.0.0, but don't break compatibility with previous frameworks, which were compatibility version 1.0.0