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/routing/binlog/blr.h

@@ -1,3 +1,4 @@
+#pragma once
 #ifndef _BLR_H
 #define _BLR_H
 /*
@@ -37,6 +38,7 @@
  *
  * @endverbatim
  */
+#include <maxscale/cdefs.h>
 #include <maxscale/dcb.h>
 #include <maxscale/buffer.h>
 #include <pthread.h>
@@ -46,6 +48,8 @@
 #include <zlib.h>
 #include <maxscale/protocol/mysql.h>
 
+MXS_BEGIN_DECLS
+
 #define BINLOG_FNAMELEN         255
 #define BLR_PROTOCOL            "MySQLBackend"
 #define BINLOG_MAGIC            { 0xfe, 0x62, 0x69, 0x6e }
@@ -676,4 +680,6 @@ extern bool blr_send_event(blr_thread_role_t role,
                            REP_HEADER *hdr,
                            uint8_t *buf);
 
+MXS_END_DECLS
+
 #endif