Cleanup header files

- All now include maxscale/cdefs.h as the very first file.
- MXS_[BEGIN|END]_DECLS added to all C-headers.
  Strictly speaking not necessary for private headers, but
  does not hurt either.
- Include guards moved to the very top of the file.
- #pragma once added.

server/modules/include/binlog_common.h

@@ -1,5 +1,6 @@
-#ifndef BINLOG_COMMON_H
-#define BINLOG_COMMON_H
+#pragma once
+#ifndef _BINLOG_COMMON_H
+#define _BINLOG_COMMON_H
 /*
  * Copyright (c) 2016 MariaDB Corporation Ab
  *
@@ -13,9 +14,13 @@
  * Public License.
  */
 
+#include <maxscale/cdefs.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <time.h>
+
+MXS_BEGIN_DECLS
+
 /**
  * Packet header for replication messages
  */
@@ -45,4 +50,6 @@ bool binlog_next_file_exists(const char* binlogdir, const char* binlog);
 uint32_t extract_field(uint8_t *src, int bits);
 const char* binlog_event_name(int type);
 
+MXS_END_DECLS
+
 #endif /* BINLOG_COMMON_H */