Address a build warning and a complaint

topl.c
..\win\tty\topl.c(595) : warning C4101: 'ln' : unreferenced local variable

win/share/tile.h

@@ -1,7 +1,7 @@
 /* NetHack 3.5  tile.h       $Date$  $Revision$ */
 typedef unsigned char pixval;
 
-typedef struct pixel_t {
+typedef struct pixel_s {
     pixval r, g, b;
 } pixel;
 

win/tty/topl.c

@@ -592,7 +592,6 @@ msghistory_snapshot(purge)
 boolean purge;		/* clear message history buffer as we copy it */
 {
     nhwchar *mesg;
-    unsigned ln;
     int i, inidx, outidx;
     struct WinDesc *cw;