Fix an assortment of compiler warnings.

A few potential bugs were removed in the process.  Much code cleanup
remains to be done.

xrogue/maze.c

@@ -21,7 +21,7 @@ struct cell {
         char x_pos;
 };
 struct b_cellscells {
-        char num_pos;           /* number of frontier cells next to you */
+        unsigned char num_pos;  /* number of frontier cells next to you */
         struct cell conn[4];    /* the y,x position of above cell */
 } b_cells;