Build main window with sdl.png.h.
PNG data to display the SDL logo.
Move member "id" to protected.
Clean doxygen generated files.
Add svn:ignore property for "doxygen".
Add documentation.
Add rule to make "docs" for creating doxygen documentation.
Add "doc" folder for documentation.
Add Doxyfile for creating documentation with doxygen.
Clean up installation. Make some commands more verbose.
