[MINOR] move error codes to common/errors.h

It's useful to be able to share error codes between C files,
so move the codes currently only used in protocols to a generic
file.
diff --git a/include/common/errors.h b/include/common/errors.h
new file mode 100644
index 0000000..4877310
--- /dev/null
+++ b/include/common/errors.h
@@ -0,0 +1,46 @@
+/*
+  include/common/errors.h
+  Global error macros and constants
+
+  Copyright (C) 2000-2007 Willy Tarreau - w@1wt.eu
+  
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation, version 2.1
+  exclusively.
+
+  This library is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with this library; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#ifndef _COMMON_ERRORS_H
+#define _COMMON_ERRORS_H
+
+/* These flags may be used in various functions which are called from within
+ * loops (eg: to start all listeners from all proxies). They provide enough
+ * information to let the caller decide what to do. ERR_WARN and ERR_ALERT
+ * do not indicate any error, just that a message has been put in a shared
+ * buffer in order to be displayed by the caller.
+ */
+#define ERR_NONE	0x00	/* no error, no message returned */
+#define ERR_RETRYABLE	0x01	/* retryable error, may be cumulated */
+#define ERR_FATAL	0x02	/* fatal error, may be cumulated */
+#define ERR_ABORT	0x04	/* it's preferable to end any possible loop */
+#define ERR_WARN	0x08	/* a warning message has been returned */
+#define ERR_ALERT	0x10	/* an alert message has been returned */
+
+
+#endif /* _COMMON_ERRORS_H */
+
+/*
+ * Local variables:
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ * End:
+ */