* 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/cygwin.din

@@ -10,6 +10,9 @@ __ctype_ptr__ DATA
 __cygwin_environ DATA
 __cygwin_user_data DATA
 _daylight DATA
+error_message_count DATA
+error_one_per_line DATA
+error_print_progname DATA
 h_errno DATA
 _impure_ptr DATA
 in6addr_any DATA
@@ -389,6 +392,8 @@ erff NOSIGFE
 _erff = erff NOSIGFE
 err SIGFE
 __errno NOSIGFE
+error SIGFE
+error_at_line SIGFE
 errx SIGFE
 euidaccess SIGFE
 execl SIGFE