Remove redundant prototype for gen_highpart.

From-SVN: r6380

gcc/optabs.c

 /* Expand the basic unary and binary arithmetic operations, for GNU compiler.
-   Copyright (C) 1987, 1988, 1992, 1993 Free Software Foundation, Inc.
+   Copyright (C) 1987, 1988, 1992, 1993, 1994 Free Software Foundation, Inc.
 
 This file is part of GNU CC.
 
@@ -192,9 +192,6 @@ rtx fixunstfsi_libfunc;
 rtx fixunstfdi_libfunc;
 rtx fixunstfti_libfunc;
 
-/* from emit-rtl.c */
-extern rtx gen_highpart ();
-
 /* Indexed by the rtx-code for a conditional (eg. EQ, LT,...)
    gives the gen_function to make a branch to test that condition.  */