Amiga: collapse #ifndef CROSS_TO_AMIGA include forks

Every #include block had a paired NH: assign path for native builds.
Only the cross-compile path is built now.

sys/amiga/winstr.c

@@ -2,15 +2,9 @@
 /* Copyright (c) Gregg Wonderly, Naperville, Illinois,  1991,1992,1993. */
 /* NetHack may be freely redistributed.  See license for details. */
 
-#ifndef CROSS_TO_AMIGA
-#include "NH:sys/amiga/windefs.h"
-#include "NH:sys/amiga/winext.h"
-#include "NH:sys/amiga/winproto.h"
-#else
 #include "windefs.h"
 #include "winext.h"
 #include "winproto.h"
-#endif
 /* Put a string into the indicated window using the indicated attribute */
 
 void