Improve CMake library detection modules

- Use standard FIND_PACKAGE_HANDLE_STANDARD_ARGS instead of custom code
- Fix reporting not found dependencies (was broken due to SDL2_ttf vs.
  SDL2_TTF), FIND_PACKAGE_HANDLE_STANDARD_ARGS handles this gracefully
Implement Width/Height/Size getters for Texture and Surface
Use size getters
Add outline to font demo
Add Point memberwise division/multiplication
Add test for Point/Rect construction and comparison from/with corresponding SDL objects
Add test for multiplication/division
Implement Rect::Contains(Rect), add corresponding test
Remove unused includes
Add various Rect constructors
Add Rect intersection and union methods
Simplify logic
Update Rect tests
Apply libstdc++ fix present in later versions of gcc 4.8

Without this clang build fails
Merge branch 'point-rect'
Merge branch 'travis-fix'
Merge branch 'size-getters'
Merge branch 'cmake-fix'