Fix #50444: PDO-ODBC changes for 64-bit

This bug is also referenced in
[#61777](https://bugs.php.net/bug.php?id=61777) and is still present in
the latest stable release of the 5.5 branch. I see two tickets exist for
this problem already, and I'm just submitting these changes via github
as a reminder that this is a serious problem for anyone using PDO_ODBC
on the x64 builds.