Bumping lightning to 1.0b5 so it works with Thunderbird 6.0.1

[Lawrence Stewart]

Hi Gecko team,

The update from Thunderbird 6.0 to 6.0.1 has stopped the Lightning 
1.0b5pre plugin from working - it claims to be incompatible with the new 
version of Thunderbird and can't be enabled. Lightning 1.0b5 seems to 
work fine with Thunderbird 6.0.1 on my wife's windows PC, so I'm 
guessing a very minor bump to the lightning build source is needed to 
get it working again.

If you're aware of this issue then great, but if not, just wanted to 
bring it to your attention so that it's on your radar.

Your work keeping all this moving parts up to date is really appreciated.

Cheers,
Lawrence