refactor error message-related functions

split message print fuctions (mpr_*), strerrno, and mscp_get/set_error
into print.c/h and strerrno.c/h.

ToDo: revise usages of priv_set_errv and pr_* functions.

src/print.h

@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+#ifndef _PRINT_H_
+#define _PRINT_H_
+
+#include <libgen.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+
+#include <mscp.h>
+
+/* message print. printed messages are passed to application via msg_fd */
+void set_print_severity(int severity);
+int get_print_severity();
+
+#define __print(fp, severity, fmt, ...)					\
+	do {								\
+		if (severity <= get_print_severity()) {		\
+			fprintf(fp, "\r\033[K" fmt "\n", ##__VA_ARGS__);	\
+			fflush(fp);					\
+		}							\
+	} while (0)
+
+#define pr_err(fmt, ...)					\
+	__print(stderr, MSCP_SEVERITY_ERR, fmt, ##__VA_ARGS__)
+#define pr_warn(fmt, ...)					\
+	__print(stderr, MSCP_SEVERITY_WARN, fmt, ##__VA_ARGS__)
+#define pr_notice(fmt, ...)				\
+	__print(stdout, MSCP_SEVERITY_NOTICE, fmt, ##__VA_ARGS__)
+#define pr_info(fmt, ...)					\
+	__print(stdout, MSCP_SEVERITY_INFO, fmt, ##__VA_ARGS__)
+#define pr_debug(fmt, ...)					\
+	__print(stdout, MSCP_SEVERITY_DEBUG, fmt, ##__VA_ARGS__)
+
+#endif /* _PRINT_H_ */