Implement SMAA T2x

[vanruesc]

Description

Add support for T2x to SMAAEffect. The goal is to use one past frame to reduce shimmering and pixel crawl.

References:

• http://iryoku.com/aacourse/downloads/13-Anti-Aliasing-Methods-in-CryENGINE-3.pdf
• https://github.com/iryoku/smaa/blob/71c806a838bdd7d517df19192a20f0c61b3ca29d/SMAA.hlsl#L195-L228

Tasks

• Implement T2x.
• Update smaa demo.

Implementation Details

• Should be done after GBuffer.VELOCITY is implemented.
• Use G-Buffer components (velocity).