Added support for DXT1/3/5 and BC5/7 compressed textures via love.image.CompressedData. Some internals are still iffy.

- added a new CompressedData type to love.image
- added love.image.isCompressed(file or data)
- love.graphics.newImage automatically tests for compression when loading a file
- added love.graphics.isSupported strings for DXT, BC5, and BC7

Compressed textures meant to be used on the GPU offer huge performance gains when
- loading the texture from a file
- loading the texture from RAM to VRAM
- loading mipmaps
- rendering

--HG--
branch : image-CompressedData

src/modules/image/wrap_Image.h

@@ -24,14 +24,16 @@
 // LOVE
 #include "Image.h"
 #include "wrap_ImageData.h"
+#include "wrap_CompressedData.h"
 
 namespace love
 {
 namespace image
 {
 
-int w_getFormats(lua_State *L);
 int w_newImageData(lua_State *L);
+int w_newCompressedData(lua_State *L);
+int w_isCompressed(lua_State *L);
 extern "C" LOVE_EXPORT int luaopen_love_image(lua_State *L);
 
 } // image