This should also be a little bit faster.

Remove some uncessary code and use more descriptive parameter names. Note that
max_vertex_idx isn't the same as "minIndex + calculatedNumberOfindices - 1"
but rather "minIndex + numberOfVertices - 1". calculatedNumberOfindices just
specifies the number of vertices that's drawn, while numberOfVertices
specifies the range of vertices that's drawn.

winapi_test: The real tests are done at compile time so use C_ASSERT() instead of ok(). Do only one test per line so one can know exactly what went wrong.