Things to add in the next alpha version
(most of them require callbacks usage):

0. Add more comments and move existing ones
   to the more appropriate places. Write more
   clean documentation.

1. Authorization API
2. Custom functions and aggregates API
3. Tracing API (sqlite_trace) 
4. Handling of busy state (sqlite_busy_handler, sqlite_busy_timeout)

5. Bindings for various functions (should be straightforward):

sqlite_interrupt
sqlite_complete
sqlite_lib_version
sqlite_libencoding

6. Replace raising of Sqlite_error with RC_misuse with Invalid_argument exception (maybe).
