New buff framework (player implementation)

Get rid of `iConditionBitFlag` in favor of a system of individual buff
objects that get composited to a bitflag on-the-fly.
Buff objects can have callbacks for application, expiration, and tick,
making them pretty flexible. Scripting languages can eventually use
these for custom behavior, too.

TODO:
- Get rid of bitflag in BaseNPC
- Apply buffs from passive nano powers
- Apply buffs from active nano powers
- Move eggs to new system
- ???

src/core/Defines.hpp

@@ -118,6 +118,13 @@ enum {
     ECSTB__END = 26,
 };
 
+enum {
+	ETBU_NONE = 0,
+	ETBU_ADD = 1,
+	ETBU_DEL = 2,
+	ETBU_CHANGE = 3
+};
+
 enum {
     SUCC = 1,
     FAIL = 0,