Add repeat=false to books in Brothers' Lair maps

This fixes a bug where the player couldn't get past the bookcase door in
the Ice Hall. Previously, pressing ACCEPT near that door would
continuously trigger one of the two nearby books.
Chinese by lonsine
Fixes to CMakeLists

* Remove BINDIR, as we don't need it
* Move "flare-game" from the DATADIR variable to the INSTALL command,
like it's done for "default" in flare-engine
Add aim_assist to alpha_demo's engine/misc.txt
Merge pull request #323 from dorkster/fixes

Cmake cleanup and aim_assist for alpha_demo
Merge pull request #322 from dorkster/books

Add repeat=false to books in Brothers' Lair maps