Fix some warnings

Remove an unused variable, add missing FALLTHRUs, and use the same
FALLTHRU wording where it wasn't recognized by gcc

win/tty/termcap.c

@@ -1171,6 +1171,7 @@ int n;
     case ATR_ULINE:
         if (nh_US)
             return nh_US;
+        /*FALLTHRU*/
     case ATR_BOLD:
     case ATR_BLINK:
 #if defined(TERMLIB) && defined(TEXTCOLOR)
@@ -1192,6 +1193,7 @@ int n;
     case ATR_ULINE:
         if (nh_UE)
             return nh_UE;
+        /*FALLTHRU*/
     case ATR_BOLD:
     case ATR_BLINK:
         return nh_HE;

win/tty/wintty.c

@@ -1527,7 +1527,7 @@ winid window;
     case NHW_MAP:
         /* cheap -- clear the whole thing and tell nethack to redraw botl */
         context.botlx = 1;
-    /* fall into ... */
+        /*FALLTHRU*/
     case NHW_BASE:
         clear_screen();
         break;
@@ -1917,7 +1917,8 @@ struct WinDesc *cw;
             /* special case: '0' is also the default ball class */
             if (!counting && index(gacc, morc))
                 goto group_accel;
-        /* fall through to count the zero */
+            /* fall through to count the zero */
+            /*FALLTHRU*/
         case '1':
         case '2':
         case '3':
@@ -2197,6 +2198,7 @@ boolean blocking; /* with ttys, all windows are blocking */
             tty_display_nhwindow(WIN_MESSAGE, TRUE);
             return;
         }
+        /*FALLTHRU*/
     case NHW_BASE:
         (void) fflush(stdout);
         break;