Highlight the sides as well as the top of a tower when it's

selected. I think this is a more or less aesthetically neutral
change for the actual selection, but the selection code is reused to
draw the victory flash and that's greatly improved by not having the
tower sides remain unflashed.

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@8843 cda61777-01e9-0310-a592-d414129be87e