Tweak CNShared

* Separate pruning frequency from timeout
* Pluralize CNShared map: login -> logins
* Increase connection timeout to 15 minutes
* Do not deallocate a nullptr in playerEnter()
* Kill connections rejected by playerEnter()
* Remove redundant inclusions of mutex headers in a few places

src/db/internal.hpp

@@ -3,12 +3,6 @@
 #include "db/Database.hpp"
 #include <sqlite3.h>
 
-#if defined(__MINGW32__) && !defined(_GLIBCXX_HAS_GTHREADS)
-    #include "mingw/mingw.mutex.h"
-#else
-    #include <mutex>
-#endif
-
 extern std::mutex dbCrit;
 extern sqlite3 *db;