Add Retina support

[focalstrategy]

In my admittedly limited testing, it seems that the favicon is always drawn at 16x16, even on retina screens where it should be 32x32 if the favicon is large enough.

Would be lovely if that worked :)

[tommoor]

Agreed, unfortunately I don't have a retina screen to test on but would love to see this update :-)

[tsuyoshizawa]

@tommoor I found cloned repository. https://github.com/lancee/tinycon
The repository is supported retina using devicePixelRatio. I confirmed it.

You can apply the changed code.

[tommoor]

Thanks, closed by 353f493