As stated on the Sqlite website :
Foreign key constraints are disabled by default (for backwards compatibility), so must be enabled separately for each database connection separately. (Note, however, that future releases of SQLite might change so that foreign key constraints enabled by default. Careful developers will not make any assumptions about whether or not foreign keys are enabled by default but will instead enable or disable them as necessary.)
This patch is just convenience functions for sqlite to enable or disable foreign keys when using a sqlite database.

bool CL_SqliteConnection::sqlite_is_foreign_keys_enabled(); // True if foreign_keys are enabled
void CL_SqliteConnection::sqlite_enable_foreign_keys(); // enables foreign keys
void CL_SqliteConnection::sqlite_disable_foreign_keys(); //disables foreign keys

Edit : Seems that there is a +#include <memory> that shouldn't be there, probably because i wrote the patch from CL 2.2.5. has to be removed i guess.