fix issue #443 #139 spool send event result

Here is a PR for issues #443 and #139.

We've added a new result status in SendEvents with code 0x11 (RESULT_PENDING | RESULT_SPOOLED). It seems logical to us because this status lies between those two status.

The SpoolTransport now set RESULT_SPOOLED instead of RESULT_SUCCESS in order to be able to make the difference between a spooled mail and a sent mail.

Unit tests fails, but it wasn't due to anything that we've added. The master branch unit tests was already broken when we cloned the project.