Ensure Virtual tables can be declared outside rusqlite crate

Not sure it is the way to go.

src/lib.rs

@@ -75,7 +75,7 @@ use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
 use std::os::raw::{c_int, c_char};
 
 use types::{ToSql, ValueRef};
-use error::{error_from_sqlite_code, error_from_handle};
+use error::error_from_handle;
 use raw_statement::RawStatement;
 use cache::StatementCache;
 
@@ -91,7 +91,7 @@ pub use transaction::{DropBehavior, Savepoint, Transaction, TransactionBehavior}
 
 #[allow(deprecated)]
 pub use error::SqliteError;
-pub use error::Error;
+pub use error::{Error, error_from_sqlite_code};
 pub use ffi::ErrorCode;
 
 pub use cache::CachedStatement;