This is an huge refactor to avoid handling Allegro FONT directly. Some
changes:
* Add she::System::defaultDisplay/Font, createRgbaSurface, loadSurface,
and loadRgbaSurface.
* Rename she::CreateSystem/Instance to she::create_system/instance.
* Remove ui/font.cpp and move ui/fontbmp.cpp to she library.
* ui::IButtonIcon uses she::Surface instead of BITMAP.
* Rename she::LockedSurface::drawAlphaSurface -> drawRgbaSurface
* Rename ui::SetDisplay -> set_display
* Rename _ji_font_text_len -> ui::Graphics::measureUIStringLength
