More versatile support for Mac attachments

[ben@…]

I implemented three new configuration options, having to do with treatment of attachments that include Mac-specific data.

The attached diff is relative to the changes I submitted in #105.

binhex

The BinHex encoding format is deprecated (in favor of AppleDouble MIME, see RFC 1740), but some older clients might still be using it. A file encoded with BinHex is annoying to decode unless you are on a Mac.

The binhex option can be set to one of:

• 'keep', in which case attachments encoded with BinHex will be included in the ticket
• 'warn', in which case attachments encoded with BinHex will be ignored, but a warning message to that effect will be included in the ticket description
• 'drop', in which case attachments encoded with BinHex will be silently ignored

The default is 'warn'.

applesingle

Same options and meaning as for binhex option above.

appledouble

The AppleDouble encoding format is the recommended way to include Mac-specific data in a MIME message, as per RFC 1740. A file encoded with AppleDouble can easily be presented usefully on all platforms.

The applesingle option can be set to one of:

• 'keep', in which case both the platform-neutral data and the Mac-specific data will be included in the ticket (as two separate attachments)
• 'warn', in which case only the platform-neutral file data will be included in the ticket. Mac-specific data will be left out, but a warning message will be included in the ticket description.
• 'strip', in which case only the platform-neutral file data will be included in the ticket. Mac-specific data will be left out with no warning.

The default is 'warn'.

[bromine]

Applied to trunk -- changeset:238