This fixes many typos in comments and one in a user-visible string (msgid "center abscisse" changed to "center abscissa" in affected po files. too).
because it confuses gtk-doc and breaks some links. Also change the "Index of new symbols in GIMP 2.x" sections to be what seems to be the modern standard (looked at the GLib and GTK+ docs), and update some other stuff.
because image.pdb is way too large.
