Tourists gain experience by seeing new types of creatures up close

Experience equivalent to killing a monster is gained when starting a turn
adjacent to and being able to see the monster.

Breaks saves.

Idea and parts of code via dNetHack

include/hack.h

@@ -673,6 +673,7 @@ struct mvitals {
     uchar born;
     uchar died;
     uchar mvflags;
+    Bitfield(seen_close, 1);
 };