Enusure that my_global.h is included first

- Added sql/mariadb.h file that should be included first by files in sql
  directory, if sql_plugin.h is not used (sql_plugin.h adds SHOW variables
  that must be done before my_global.h is included)
- Removed a lot of include my_global.h from include files
- Removed include's of some files that my_global.h automatically includes
- Removed duplicated include's of my_sys.h
- Replaced include my_config.h with my_global.h

plugin/handler_socket/libhsclient/auto_addrinfo.hpp

@@ -9,8 +9,7 @@
 #ifndef DENA_AUTO_ADDRINFO_HPP
 #define DENA_AUTO_ADDRINFO_HPP
 
-#include <my_config.h>
-#include <sys/types.h>
+#include <my_global.h>
 #include <sys/socket.h>
 #include <netdb.h>
 #include <string.h>

plugin/handler_socket/libhsclient/hstcpcli.cpp

@@ -6,8 +6,7 @@
  * See COPYRIGHT.txt for details.
  */
 
-#include <my_config.h>
-
+#include <my_global.h>
 #include <stdexcept>
 
 #include "hstcpcli.hpp"

plugin/handler_socket/libhsclient/socket.cpp

@@ -6,13 +6,10 @@
  * See COPYRIGHT.txt for details.
  */
 
-#include <my_config.h>
+#include <my_global.h>
 
 #include <stdexcept>
 #include <string.h>
-#include <errno.h>
-#include <unistd.h>
-#include <fcntl.h>
 #include <signal.h>
 #include <sys/un.h>