* cygwin.din (error): Export.

(error_at_line): Export.
(error_message_count): Export.
(error_one_per_line): Export.
(error_print_progname): Export.
* errno.cc (error_message_count): Define.
(error_one_per_line): Define.
(error_print_progname): Define.
(_verror): New static function.
(error): New function.
(error_at_line): New function.
* posix.sgml (std-gnu): Add error, error_at_line.
* include/error.h: New header.
* include/cygwin/version.h (CYGWIN_VERSION_API_MINOR): Bump.

winsup/cygwin/include/error.h

@@ -0,0 +1,30 @@
+/* error.h: GNU error reporting functions
+
+   Copyright 2011 Red Hat, Inc.
+
+This file is part of Cygwin.
+
+This software is a copyrighted work licensed under the terms of the
+Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
+details. */
+
+#ifndef _ERROR_H
+#define _ERROR_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+void error (int, int, const char *, ...);
+void error_at_line (int, int, const char *, unsigned int, const char *, ...);
+
+extern unsigned int error_message_count;
+extern int error_one_per_line;
+extern void (*error_print_progname) (void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _ERROR_H */