This reverts commit 492e1ab5,
but keeps the code cleanups, and adds some more.

and add a PDB compat procedure.

like in the iwarp plug-in. I consider the plug-in obsolete now.

which multiplies each float in a gegl_format_n(float, n) input
by a factor.

See bug 734879: commits c87c5cd in GTK+ master, and 03c5335 in gtk-2-24
branch.

Save the active tag filter in sessionrc.

If there is no gimp-[brush|pattern|brush-pipe]-name parasite,
default to the file's basename without extension, instead of
always "GIMP Brush" etc.

Also clean up the code, and make the plug-ins do the same things the
same way.

Set the "activates-default" property on the spinbutton and entry in
the file-gbr-save dialog.

...bring focus back to GIMP image window

When showing docks in multi-window-mode, try to set the keyboard focus
back to the active display because it might have been stolen by a dock.

The loop was right, but the following if was meant to check if
the token was terminated correctly so it needs to be *p.

Change gimp_brush_generated_get_half_size() to get_size() and
calculate its exact size in float. This is really a minor change that
seems to work well.

- add gimp_image_get,get_xcf_compat_mode()
- add a compat toggle to GimpFileDialog which is shown and sensitive
  only for a save (not export), and if the image structure allows
  to save an old version at all. The button also has a tooltip
  which explains why it is sensitive and what it does
- add "gboolean xcf_compat" to file_save_dialog_save_image()
- in file_save_dialog_save_image(), call image_set_xcf_compat_mode(TRUE)
  only around the call to file_save() and set it to FALSE after saving
- in xcf_save_invoker(), honor the image's XCF compat flag and save an
  RLE-compressed XCF if possible

The above is very convoluted and doesn't pass the "xcf_compat" boolean
directly because we can't change the parameters of gimp-xcf-save, and
because the gimp-xcf-save might be called indirectly.

XCF spec:
- Update to GIMP 2.8.10
- Clarify role of file formats in the save-vs.-export-context
- Rearrange outline
- Collect infos on basic concepts in one chapter
- Add table of contents
- Add File format version history
- Add note on image size
- Add open questions and TODOs
- Sort properties alphabetically
- Unify tiles and hierarchy examples
- Wording
- Cosmetic cleanups

Extract compositing.txt from xcf.txt

Update parasites.txt:
- Replace SVN->Git
- Update contact e-mail address
- Add table of contents

Cherry-picked from commit a83791be