[MERGE] Support Claws as a mail client.

[Aaron Bentley]

Aaron Bentley has voted tweak.
Status is now: Conditionally approved
Comment:
Looks fine, and if it makes Claws more usable than xdg-email would, it's 
definitely worth having in the core.  xdg-email doesn't work properly 
with Thunderbird either.

I'll apply the µ patch and submit.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C20090106111132.04788b27%40bungo%3E
Project: Bazaar