Update bitcoin icon to make nsis setup exe deterministic.
Update bitcoin icon to make nsis setup exe deterministic.

This adds a 32x32 16-bit icon to the bitcoin.ico file.
Though this realistically probably looks worse than the 32-bit
32x32 being displayed on a 16-bit monitor, it makes the nsis
setup exe deterministic in gitian output (go figure) which makes
the slight visual loss for users of very old monitors/computers
worth it.

azilber/devcoin,azilber/devcoin,azilber/devcoin