Need to be able to control value of UseNonZeroWinding

[Zyl9393]

Over at golang#90 some discussion has been happening regarding incorrectly rendered glyphs. It appears (?) that true type fonts should generally set UseNonZeroWindOrder = true on the rasterizer. However, the rasterizer is inaccessible on instances of truetype.Face as well as in freetype.Context. Unless anyone knows more, we should make these accessible, i.e. change r to R in both structs. The value does not control any generated data and can be changed at any time between rasterization of glyphs.

[rcoreilly]

sounds good -- will do so soon..

[rcoreilly]

It was a lot simpler to just set UseNonZeroWindOrder = true on the rasterizer when it is first created. I verified that this fixes the issue -- Apple Chancery euro symbol had it, for example.

[Zyl9393]

As I said, not sure if a font could require even-odd winding order. The change does work for me, though. Thanks.