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.
Add Gold item
change speeds to tiles per second
adapt melee_range to a tile unit
adapt thread_range to tile units
change autopickup_range and powers range to tile based units
change radius of powers to tile based
Add sfx/animations to gold loot and set currency_id
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
Merge remote-tracking branch 'mainline/master' into floatingpointmovement
Merge remote-tracking branch 'upstream/master' into currency

Conflicts:
	mods/alpha_demo/engine/misc.txt
Remove obsolete data from engine/loot.txt
Fix copy-paste error for coin animations
Merge pull request #324 from dorkster/currency

Gold as an item
Merge remote-tracking branch 'mainline/master' into floatingpointmovement
Add gold icon artwork & increase gold stack max to 5000
Merge pull request #326 from dorkster/currency

Add gold icon artwork & increase gold stack max to 5000