Evas GL: Add hidden flags instead of env vars

Evas GL: Add hidden flags instead of env vars

For Direct Override and Memory Optimization.
This commit includes a lot of changes, but most of them
are directly related to moving the global var into the surface.
In particular, we must keep track of the DR surfaces, so we
add them to a hash indexed by texture id.

Change-Id: Iea696e279eac7e4ab4d130adb748936f2d97488c