Minor update to MIME type checking rules, to allow more legal MIME
types.
Made the multipart detection code less aggressive, in small text
messages it would mistake common ascii-graphic signatures for message
boundaries and mess up the parsing quite badly.
Made the filename checker check ALL possible file names against
each rule, instead of just checking the "default" one. If
feat_mime_files is set, then the default file-name for that mime
type will be checked as well. This is a major improvement to
security, but requires that filename rules are ordered so that
that all DROP/DEFANG/MANGLE rules precede any ACCEPT rules.
Made the sanitizer read /etc/mime.types (if it exists) to generate a
more complete list of default filenames for unnamed parts.
Anomy Sanitizer filters mail messages checking for common exploits and
hostile file attachments. For instance: it can remove attachments,
rename unknown file types, "defang" HTML messages, fix MIME headers,
and call external virus scanners to scan email attachments.
