[DejaVu-fonts] Double-struck letters

[Nocturnal D. <noc...@gm...>]

Hi,

Sorry for the delay, but I have now committed the most important of the 
double-struck symbols. As with other math letters/symbols we had so far 
there are both normal and (just slightly) bold versions and no oblique ones.

Please review them and let me know if there are any problems.

Regards,
Gee Fung Sit