Extend MetaFrameBorders to include shadow and resize borders to
calculate invisible border size. Also added border caching to prevent
recalculating borders on every frame operation.

This is a backport of the following commits from Metacity:
- https://gitlab.gnome.org/GNOME/metacity/-/commit/21e664af
- https://gitlab.gnome.org/GNOME/metacity/-/commit/3c6e269b
- https://gitlab.gnome.org/GNOME/metacity/-/commit/700e87ea

find . \( -name '*.h' -o -name '*.c' \) -exec sed -i 'N;/^\n$/D;P;D;' {} \;

https://bugzilla.gnome.org/show_bug.cgi?id=628195

upstream commit:
https://gitlab.gnome.org/GNOME/metacity/commit/3994d7a0

An ARGB window with a frame is likely something like a transparent
terminal. It looks awful (and breaks transparency) to draw a big
opaque black shadow under the window, so clip out the region under
the terminal from the shadow we draw.

Add meta_window_get_frame_bounds() to get a cairo region for the
outer bounds of the frame of a window, and modify the frame handling
code to notice changes to the frame shape and discard a cached
region. meta_frames_apply_shapes() is refactored so we can extract
meta_frames_get_frame_bounds() from it.

https://bugzilla.gnome.org/show_bug.cgi?id=635268

NOTE: Applied only partially, compositor part is still missing...

upstream commit:
https://gitlab.gnome.org/GNOME/metacity/commit/0f2e32d1

upstream commit:
https://gitlab.gnome.org/GNOME/metacity/commit/5404d8f2

There were actually *two* MetaFrameGeometry structs: one in theme-private.h,
one in frame.h. The latter public struct was populated by a mix of (void*)
casting and int pointers, usually pulling directly from the data in the private
struct.

Remove the public struct, replace it with MetaFrameBorders and scrap all
the pointer hacks to populate it, instead relying on both structs being used
in common code.

This commit should be relatively straightforward, and it should not do any
tricky logic at all, just a sophisticated find and replace.

https://bugzilla.gnome.org/show_bug.cgi?id=644930

upstream commit: https://gitlab.gnome.org/GNOME/metacity/commit/72224a165
NOTE: Patch copied from metacity and adapted for marco.

Just run:
 $ find -name '*.c' -print0 | xargs -r0 sed -e 's/[[:blank:]]\+$//' -i
 $ find -name '*.h' -print0 | xargs -r0 sed -e 's/[[:blank:]]\+$//' -i