#324 Misleading text about needed key in Enigmail security info

[Ludwig Hügelschäfer]

https://lists.enigmail.net/pipermail/enigmail-users_enigmail.net/2014-September/002010.html

What happens:

Enigmail Security Info

Error - signature verification failed
Public key <64-bit-KeyId> __needed__ to verify signature

BAD signature from <user>

As the key is not "needed" any more, as it is already in the keyring, it should be:

Enigmail Security Info

Error - signature verification failed
Public key <64-bit-KeyId> __used__ to verify signature

BAD signature from <user>

[Patrick Brunschwig]

Ludwig's patch included on master.