Remove 'absolute' draw mode.

Absolute draw mode is identical to disabling blending, and we already
support turning off blending.  So let's just do that.
Add basic support for window resizing (disabled)

Need to set up an API for setting that our window should be resizable,
as it requires work on the part of a client to support, so probably
shouldn't be on by default.
Immediately set vsTween to destinatino for 0-time tweens.