add a set of decals to stock tileset

win/share/decals.txt contains (initially) a decal_delimiter tile,
a decal_pet tile, and a decal_pile tile.
The latter two can be used for hilite_pet and hilite_pile implementations
that don't have something in place already. The implementation would
just need to apply (merge) the non-background decal pixels over a
regular tile.

The special decal_delimiter tile can be used to confirm the presence
of the delimiter tiles in the tileset and mark the end of the regular tiles,
and the start of the decal tiles.
   row 1 contains the background color whose pixels should be
   ignored when applying a decal to a tile.
   row 2 contains a row of pixels colored (0, 0, 0).
   row 3 contains a row of pixels colored pure green (0, 255, 0).
   row 3 contains a row of pixels colored pure blue  (0, 0, 255).

win/share/decals.txt

@@ -0,0 +1,95 @@
+# decals.txt - definitions for 'decals'
+# to merge over top of another tile
+#
+#  Note: lines beginning with '# tile ' are not comments; other
+#  lines beginning with '#' are.
+. = (71, 108, 108)
+A = (0, 0, 0)
+B = (0, 182, 255)
+C = (255, 108, 0)
+D = (255, 0, 0)
+E = (0, 0, 255)
+F = (0, 145, 0)
+G = (108, 255, 0)
+H = (255, 255, 0)
+I = (255, 0, 255)
+J = (145, 71, 0)
+K = (204, 79, 0)
+L = (255, 182, 145)
+M = (237, 237, 237)
+N = (255, 255, 255)
+O = (215, 215, 215)
+P = (108, 145, 182)
+Q = (18, 18, 18)
+R = (54, 54, 54)
+S = (73, 73, 73)
+T = (82, 82, 82)
+U = (205,205,205)
+V = (104, 104, 104)
+W = (131, 131, 131)
+X = (140, 140, 140)
+Y = (149, 149, 149)
+Z = (195, 195, 195)
+0 = (100, 100, 100)
+1 = (72, 108, 108)
+2 = (0, 255, 0)
+# tile 0 (decal_delimiter)
+{
+  ................
+  AAAAAAAAAAAAAAAA
+  2222222222222222
+  EEEEEEEEEEEEEEEE
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+}
+# decals that can be overlayed
+# onto an object tile
+#
+# tile 1 (decal_pet)
+{
+  ............D.D.
+  ...........DDDDD
+  ............DDD.
+  .............D..
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+}
+# tile 2 (decal_pile)
+{
+  ..N.............
+  ..N.............
+  NNNNN...........
+  ..N.............
+  ..N.N...........
+  .....N..........
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+  ................
+}