Moved GIF file reading to image/, optimisation of plotting for GIFs, JNGs, PNGs and JPEGs, initial work for toolbar customisation. Possibly some other things too.
svn path=/import/netsurf/; revision=1301
Add generic bitmap functions. Move jpeg and mng code from riscos/ to image/ and update to use bitmap. Note: background tiling and drawfile export for jpeg and mng/png are broken.
svn path=/import/netsurf/; revision=1265