Directly execute scripts if script boxes have a non-empty script field

Instead of using gamestates, just directly use the 'script' attribute of
a script box if it is non-empty.

This is accomplished by having to return the index of the block that the
player collides with, so callers can inspect the 'script' attribute of
the block themselves, and do their logic accordingly.

desktop_version/src/Entity.h

@@ -105,7 +105,7 @@ public:
 
     void settemprect(int t);
 
-    int checktrigger();
+    int checktrigger(int* block_idx);
 
     int checkactivity();