New puzzle: `Light Up', by James H.

Also in this checkin (committed by mistake - I meant to do it
separately), a behind-the-scenes change to Slant to colour the two
non-touching classes of diagonals in different colours. Both colours
are set to black by default, but configuration by way of
SLANT_COLOUR_* can distinguish them if you want.

[originally from svn r6164]

Recipe

@@ -25,6 +25,7 @@ SLANT    = slant dsf
 
 ALL      = list NET NETSLIDE cube fifteen sixteen rect pattern solo twiddle
          + MINES samegame FLIP guess PEGS dominosa UNTANGLE blackbox SLANT
+         + lightup
 
 net      : [X] gtk COMMON NET
 netslide : [X] gtk COMMON NETSLIDE
@@ -44,6 +45,7 @@ dominosa : [X] gtk COMMON dominosa
 untangle : [X] gtk COMMON UNTANGLE
 blackbox : [X] gtk COMMON blackbox
 slant    : [X] gtk COMMON SLANT
+lightup  : [X] gtk COMMON lightup
 
 # Auxiliary command-line programs.
 solosolver :    [U] solo[STANDALONE_SOLVER] malloc
@@ -74,6 +76,7 @@ dominosa : [G] WINDOWS COMMON dominosa
 untangle : [G] WINDOWS COMMON UNTANGLE
 blackbox : [G] WINDOWS COMMON blackbox
 slant    : [G] WINDOWS COMMON SLANT
+lightup  : [G] WINDOWS COMMON lightup
 
 # Mac OS X unified application containing all the puzzles.
 Puzzles  : [MX] osx osx.icns osx-info.plist COMMON ALL
@@ -165,7 +168,7 @@ FORCE:
 install:
 	for i in cube net netslide fifteen sixteen twiddle \
 	         pattern rect solo mines samegame flip guess \
-		 pegs dominosa untangle blackbox slant; do \
+		 pegs dominosa untangle blackbox slant lightup; do \
 		$(INSTALL_PROGRAM) -m 755 $$i $(DESTDIR)$(gamesdir)/$$i; \
 	done
 !end