Partial port of r59682 from py3k.

Partial port of r59682 from py3k.

On Windows, when import fails to load a dll module, the message says
"error code 193" instead of a more informative text.

It turns out that FormatMessage needs additional parameters for some error codes.
For example: 193 means "%1 is not a valid Win32 application".
Since it is impossible to know which parameter to pass, we use
FORMAT_MESSAGE_IGNORE_INSERTS to get the raw message, which is still better
than the number.