Add the ability to enable and disable foreign key constraints and triggers

using calls to sqlite3_db_config().

FossilOrigin-Name: 09e167f9c14625924b17bbb1f292f89ac9ddc93a

src/sqliteInt.h

@@ -925,6 +925,7 @@ struct sqlite3 {
 #define SQLITE_AutoIndex      0x08000000  /* Enable automatic indexes */
 #define SQLITE_PreferBuiltin  0x10000000  /* Preference to built-in funcs */
 #define SQLITE_LoadExtension  0x20000000  /* Enable load_extension */
+#define SQLITE_EnableTrigger  0x40000000  /* True to enable triggers */
 
 /*
 ** Bits of the sqlite3.flags field that are used by the