Add ASIC support

[eugbaranov]

With ASIC's coming out soon I wonder how difficult would it be to implement?

[scintill]

Mining ASICs probably don't do the EC math needed for vanity generation.

[ryancdotorg]

ASIC stands for Application Specific Integrated Circuit. In the case of mining ASICs, the application is Bitcoin mining using double sha256. Double sha256 isn't useful in any way for generating vanity addresses, so this is not possible.