C++ modernize: Pragma once (#6264)

* Migrate cpp headers to pragma once

src/localplayer.h

@@ -17,8 +17,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
-#ifndef LOCALPLAYER_HEADER
-#define LOCALPLAYER_HEADER
+#pragma once
 
 #include "player.h"
 #include "environment.h"
@@ -183,5 +182,3 @@ private:
 	GenericCAO *m_cao = nullptr;
 	Client *m_client;
 };
-
-#endif