(svn r15027) -Merge: tomatos and bananas left to be, here is NoAI for all to see.

NoAI is an API (a framework) to build your own AIs in. See:
   http://wiki.openttd.org/wiki/index.php/AI:Main_Page
 With many thanks to:
  - glx and Rubidium for their syncing, feedback and hard work
  - Yexo for his feedback, patches, and AIs which tested the system very deep
  - Morloth for his feedback and patches
  - TJIP for hosting a challenge which kept NoAI on track
  - All AI authors for testing our AI API, and all other people who helped in one way or another
-Remove: all old AIs and their cheats/hacks

src/ai/api/ai_testmode.hpp

@@ -0,0 +1,48 @@
+/* $Id$ */
+
+/** @file ai_testmode.hpp Switch the AI to Test Mode. */
+
+#ifndef AI_TESTMODE_HPP
+#define AI_TESTMODE_HPP
+
+#include "ai_object.hpp"
+
+/**
+ * Class to switch current mode to Test Mode.
+ * If you create an instance of this class, the mode will be switched to
+ *   Testing. The original mode is stored and recovered from when ever the
+ *   instance is destroyed.
+ * In Test mode all the commands you execute aren't really executed. The
+ *   system only checks if it would be able to execute your requests, and what
+ *   the cost would be.
+ */
+class AITestMode : public AIObject {
+public:
+	static const char *GetClassName() { return "AITestMode"; }
+
+private:
+	AIModeProc *last_mode;
+	AIObject *last_instance;
+
+protected:
+	/**
+	 * The callback proc for Testing mode.
+	 */
+	static bool ModeProc(TileIndex tile, uint32 p1, uint32 p2, uint procc, CommandCost costs);
+
+public:
+	/**
+	 * Creating instance of this class switches the build mode to Testing.
+	 * @note When the instance is destroyed, he restores the mode that was
+	 *   current when the instance was created!
+	 */
+	AITestMode();
+
+	/**
+	 * Destroying this instance reset the building mode to the mode it was
+	 *   in when the instance was created.
+	 */
+	~AITestMode();
+};
+
+#endif /* AI_TESTMODE_HPP */