Fix an assortment of compiler warnings.

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

rogue4/passages.c

@@ -136,7 +136,7 @@ void
 conn(int r1, int r2)
 {
     register struct room *rpf, *rpt = NULL;
-    register char rmt;
+    unsigned char rmt;
     register int distance = 0, turn_spot = 0, turn_distance = 0, index;
     register int rm;
     register char direc;