Revert "[ft] Fix memory bug in copying bitmaps"

This reverts commit a0f556f37fb7016aa304b7cf0e811c0d38f0b969.

The change was clearly wrong now that I read.  I was probably
tricked by what was fixed in the follow-up commit
e738079302a968b7b1fb9101cd4d92a8887bedce.
gitignore: Ignore generated tmpl dir in public docs
clip: Do not modify the special all-clipped cairo_clip_t

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75819
clip: Fix handling of special all-clipped cairo_clip_t

_cairo_clip_intersect_box() wasn't checking if it was called with the special,
read-only all-clipped clip and thus could have ended up writing to read-only
memory.

References: https://bugs.freedesktop.org/show_bug.cgi?id=75819
Signed-off-by: Uli Schlachter <psychon@znc.in>