OpenVG binding

Copperbox revisions 675, 676 & 677.

Fixed the problem with VGHandle - the type had changed in ShivaVG 0.2.1.

Running the example now fails on Windows - runhaskell complains that the symbol _vgMask cannot be found. This is one of the several functions that weren't implemented in ShivaVG 0.2.0 and are now stubbed in 0.2.1. This makes me suspect that the runhaskell Setup.hs steps to build the Haskell binding are linking to an old library on my system, but I can't see how this can be happening.

MacOSX doesn't seem to have this problem and I'll put the 0.2 binding on Hackage once I've tested the sdist (again) on OSX.