Add AI script code to provide a cleaner API around the engine interface.

Handle AIProxy entirely through scripts.
Support structured clones of script values.
Improve performance.
Support multiple script contexts sharing a runtime.
Use a separate context per AI player.

This was SVN commit r8866.

source/scriptinterface/ScriptVal.h

@@ -40,7 +40,7 @@ public:
 	/**
 	 * Returns whether the value is JSVAL_VOID.
 	 */
-	bool undefined() const { return JSVAL_IS_VOID(m_Val); }
+	bool undefined() const { return JSVAL_IS_VOID(m_Val) ? true : false; }
 
 private:
 	jsval m_Val;