RagePhoto.h -> RagePhoto.hpp
RagePhotoA.h -> RagePhotoA.hpp
RagePhotoC.h -> RagePhoto.h
unicode.cmake: exclude codecvt for C builds
GitHub Actions: separate C and CXX builds
CMakeLists.txt: fixes for MSVC and C library support
RagePhoto: non C++11 support
RagePhotoC: clarify C instance support in comment
RagePhotoTypedefs: add typedefs for C library