vector: make args float32 pairs instead of f32.Vec2.

The f32.Vec2 type doesn't seem worth it.

Change-Id: I021c7e13d7e2dd261334f4aa7e867df4fd8f1c3e
Reviewed-on: https://go-review.googlesource.com/32772
Reviewed-by: David Crawshaw <crawshaw@golang.org>
5 files changed