mailarchive.module, saving attachments when safe_mode is on

Issue Summary

when safe_mode is on (common on ISP's), creating subdirectories and storing attachment fails when the webserver runs as another user than the owner of the scripts (for example, the ftp user).

This can be solved by manually creating the files/mailarchive directory (with permissions set to 777), and changing the _mailarchive_extract_attachments so it doesn't create month/year subdirectories