vbo: remove vbo_context.h and change includes to use vbo.h instead

Now vbo.h is the public interface to the VBO module.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>

src/mesa/vbo/vbo_exec_api.c

@@ -44,7 +44,6 @@ USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include "main/dispatch.h"
 #include "util/bitscan.h"
 
-#include "vbo_context.h"
 #include "vbo_noop.h"
 #include "vbo_private.h"