bug#15899: 24.3.50; regression: `region' overlay is lower priority than default

[Drew Adams <drew.adams@oracle.com>]

In Emacs 24.3, if you highlight some text with an overlay, without
specifying any priority for the overlay, that overlay will be lower
priority than the `region' face overlay that is used to select text for
the region.

In this build, the region overlay is of lower priority, so the other
overlay hides the region overlay.

To test, create an overlay without specifying any priority.
E.g. evaluate this in buffer *scratch* from emacs -Q.

(text-mode) ; No font lock interference.
(setq overlay  (make-overlay 20 40))
(overlay-put overlay 'face 'highlight)

Then select text in the first line, from before char 20 to after char
40.  The highlighting from 20 to 40 shows, instead of the region.

Do the same thing in Emacs 24.3 - no bug there.  Dunno when the
regression started.


In GNU Emacs 24.3.50.1 (i686-pc-mingw32)
 of 2013-11-12 on LEG570
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking 'CFLAGS=-O0 -g3' CPPFLAGS=-DGLYPH_DEBUG=1'