add message.h and message.c, mscp_set|get_error()

Instead of pr_err(), libmscp uses mscp_set_error() and
applications use mscp_get_errror() to get error message.

src/message.h

@@ -0,0 +1,32 @@
+#ifndef _MESSAGE_H_
+#define _MESSAGE_H_
+
+#include <libgen.h>
+
+enum {
+	MSCP_SEVERITY_ERR = 0,
+	MSCP_SEVERITY_WARN,
+	MSCP_SEVERITY_NOTICE,
+	MSCP_SEVERITY_INFO,
+	MSCP_SEVERITY_DEBUG,
+};
+
+/* message print. printed messages are passed to application via msg_fd */
+//void mprint_set_severity(int severity);
+//void mprint(int severity, const char *fmt, ...);
+
+#define mpr_err(fmt, ...) mprint(MSCP_SEVERITY_ERR, fmt, ##__VA_ARGS__)
+#define mpr_warn(fmt, ...) mprint(MSCP_SEVERITY_WARN, fmt, ##__VA_ARGS__)
+#define mpr_notice(fmt, ...) mprint(MSCP_SEVERITY_NOTICE, fmt, ##__VA_ARGS__)
+#define mpr_info(fmt, ...) mprint(MSCP_SEVERITY_INFO, fmt, ##__VA_ARGS__)
+#define mpr_debug(fmt, ...) mprint(MSCP_SEVERITY_DEBUG, fmt, ##__VA_ARGS__)
+
+
+/* error message buffer */
+#define mscp_set_error(fmt, ...)						\
+	_mscp_set_error("%s:%d:%s: " fmt,				\
+			basename(__FILE__), __LINE__, __func__, ##__VA_ARGS__)
+
+void _mscp_set_error(const char *fmt, ...);
+
+#endif /* _MESSAGE_H_ */