Fix 0011560: ADOdb version check in check.php is incorrect

See upstream bug report
http://phplens.com/lens/lensforum/msgs.php?id=18320 for the reason as to
why this change is necessary. version_compare works with strings, not
float values. And the Version() function in ADOdb should not be
returning floats anyway (there is no way to determine if the version if
5.1 or 5.10 from a float value).