Distorted Android

Move on to Stencil on both stages of the BLUR + separate 'blit with depth'.

This works wonders on Nexus 5X ( r=50 quality=HIGHIEST 1,4,8 cubes: 59.3,43.6,41.0 FPS! ) but it somehow fails to clear the DEPTH and STENCIL buffers on Nexus 4....

Move to a new way to detecting depth of postprocessing halos.
This switches off stenciling (hopefully temporarily!)

Use Transform Feedback to (optionally) display the Normal vectors.

Dynamic display of bounding rectangles (with coords computed by Vertex Shader and gotten with Transform Feedback) works now.

Major problem: the glMapBufferRange() slows doewn rendering in a major way. Multiblur's FPS:

Nexus5X : 35.4 before -> 12.6 after...

Make the Feedback APP work again.

Revert "Progress with TransferFeedback app - introduce two modes: USEPOINTS 'true' or 'false'."

This reverts commit 21304c55380460c5882b789ea13eb00ffd9a686c.

Revert "This commit (and reading the OpenGL ES 3.0 spec) pretty conclusively proves that, sadly, Nexus 4's Transform Feedback implementation is incomplete (doesn't work with GL_TRIANGLES primitiveMode)"

This reverts commit 5ba19814852de1762e452662a13c4944792014a9.

Revert "Some progress with Transform Feedback. Still many bugs all over."

This reverts commit 79921db22e4ff5a3b2e6e3466a39445f5607a695.

Some progress with Transform Feedback. Still many bugs all over.

This commit (and reading the OpenGL ES 3.0 spec) pretty conclusively proves that, sadly, Nexus 4's Transform Feedback implementation is incomplete (doesn't work with GL_TRIANGLES primitiveMode)