Update download link at gegl.org to point to gegl-v0.4
Update http://www.gegl.org/ the "tarball releases" destination not to be https://download.gimp.org/pub/gegl/0.3/, as 0.4 is the version required by current Gimp and first downloading and compiling 0.3 to find later, that 0.4 is required and the website link was misleading leads to lost time.