(-error:): Call objc_error function instead of using function pointer.

From-SVN: r13584

gcc/objc/Object.m

 /* The implementation of class Object for Objective-C.
-   Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc.
+   Copyright (C) 1993, 1994, 1995, 1997 Free Software Foundation, Inc.
 
 This file is part of GNU CC.
 
@@ -29,8 +29,6 @@ Boston, MA 02111-1307, USA.  */
 #include "objc/Protocol.h"
 #include "objc/objc-api.h"
 
-extern void (*_objc_error)(id object, const char *format, va_list);
-
 extern int errno;
 
 #define MAX_CLASS_NAME_LEN 256
@@ -337,7 +335,7 @@ extern size_t strlen(const char*);
                     object_is_instance(self)?"instance":"class",
                     (aString!=NULL)?aString:"");
   va_start(ap, aString);
-  (*_objc_error)(self, fmt, ap);
+  objc_error(self, OBJC_ERR_UNKNOWN, fmt, ap);
   va_end(ap);
   return nil;
 #undef FMT