Merge 'Add read implementation of user_version pragma with ReadCookie opcode' from Jonathan Webb

Just a bare bones implementation of ReadCookie and support for the
user_version pragma

Closes #909

vendored/sqlite3-parser/src/parser/ast/mod.rs

@@ -1622,6 +1622,8 @@ pub enum PragmaName {
     PageCount,
     /// returns information about the columns of a table
     TableInfo,
+    /// Returns the user version of the database file.
+    UserVersion,
     /// trigger a checkpoint to run on database(s) if WAL is enabled
     WalCheckpoint,
 }