nine: check hardware support before using vertex texture

With this nine no longer generates texturing opcodes in vextex shaders for r300 hardware that doesn't support it. This was discussed in https://github.com/iXit/wine-nine-standalone/issues/129 with @axeldavy . I hope that the code is OK, I have no clue about nine, but this should be quite trivial.

I also have no idea what is the standard testing coverage for nine patches, there is no regression with the Xnine tests (but that looks just like some basic testing) is there some testsuite like piglit for nine? With r300 it fixes the shader compile failures but I can't even test if this regresses something, since nine is still really badly broken on r300, but we are hopefully slowly getting there...