This reverts commit 833666d462.
The _pdb files are an implementation detail and we do not want
separate doc sections for them, the conflicts need so be resolved in
another way.
Otherwise we get a few duplicate sections since some of the non-PDB
files are named similarly.
Fix this GObject introspection warning and other similar warnings:
> libgimp/gimp_pdb.c:28: Warning: Gimp: multiple comment blocks
> documenting 'SECTION:gimp:' identifier (already seen at gimp.c:129).
All foo_pdb.c functions in libgimp regenerated. I have reviewed this a
dozen times, but please have a look, there might well be glitches and
our public API is sortof important...
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.
