Add parametrized exec's (esqlite3:exec/3 and esqlite3:exec/4)
Removed 'unexpected return code'; we're using the v2 version of sqlite_prepare

See http://www.sqlite.org/c3ref/step.html; any error code can be returned.
Merge pull request #7 from arjan/parametrized-exec

Add parametrized exec's (esqlite3:exec/3 and esqlite3:exec/4)