New puzzle: `Untangle', cloned (with the addition of random grid

generation) from a simple but rather fun Flash game I saw this
morning.

Small infrastructure change for this puzzle: while most game
backends find the midend's assumption that Solve moves are never
animated to be a convenience absolving them of having to handle the
special case themselves, this one actually needs Solve to be
animated. Rather than break that convenience for the other puzzles,
I've introduced a flag bit (which I've shoved in mouse_priorities
for the moment, shamefully without changing its name).

[originally from svn r6097]

Recipe

@@ -20,9 +20,10 @@ NETSLIDE = netslide tree234
 MINES    = mines tree234
 FLIP     = flip tree234
 PEGS     = pegs tree234
+UNTANGLE = untangle tree234
 
 ALL      = list NET NETSLIDE cube fifteen sixteen rect pattern solo twiddle
-         + MINES samegame FLIP guess PEGS dominosa
+         + MINES samegame FLIP guess PEGS dominosa UNTANGLE
 
 net      : [X] gtk COMMON NET
 netslide : [X] gtk COMMON NETSLIDE
@@ -39,6 +40,7 @@ flip     : [X] gtk COMMON FLIP
 guess    : [X] gtk COMMON guess
 pegs     : [X] gtk COMMON PEGS
 dominosa : [X] gtk COMMON dominosa
+untangle : [X] gtk COMMON UNTANGLE
 
 # Auxiliary command-line programs.
 solosolver :    [U] solo[STANDALONE_SOLVER] malloc
@@ -66,6 +68,7 @@ flip     : [G] WINDOWS COMMON FLIP
 guess    : [G] WINDOWS COMMON guess
 pegs     : [G] WINDOWS COMMON PEGS
 dominosa : [G] WINDOWS COMMON dominosa
+untangle : [G] WINDOWS COMMON UNTANGLE
 
 # Mac OS X unified application containing all the puzzles.
 Puzzles  : [MX] osx osx.icns osx-info.plist COMMON ALL
@@ -157,7 +160,7 @@ FORCE:
 install:
 	for i in cube net netslide fifteen sixteen twiddle \
 	         pattern rect solo mines samegame flip guess \
-		 pegs dominosa; do \
+		 pegs dominosa untangle; do \
 		$(INSTALL_PROGRAM) -m 755 $$i $(DESTDIR)$(gamesdir)/$$i; \
 	done
 !end