draw: fix overflows in the indexed rendering paths

draw: fix overflows in the indexed rendering paths

The semantics for overflow detection are a bit tricky with
indexed rendering. If the base index in the elements array
overflows, then the index of the first element should be used,
if the index with bias overflows then it should be treated
like a normal overflow. Also overflows need to be checked for
in all paths that either the bias, or the starting index location.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>