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
Fix jpeg redraw
Move png.c/h to /image and rework to use the bitmap code
Make RISC OS bitmap struct publically accessible (via riscos/bitmap.h)
Draw export now embeds JPEGs and PNGs/MNGs/JNGs correctly again.
Background images are now plotted correctly again.
svn path=/import/netsurf/; revision=1268