* Revised PerspectiveCamera.

- Allows extra skew for stereo rendering.
- Allows to query effective FOV angle (considering .zoom).
- Proper copy / serialization of all properties.
- Tidier, single code path frustum calculation.
- No longer uses ProjectionMatrix.makePerspective.

* Revised PerspectiveCamera physical interface.

See #8428.

* Triangle: new method .closestPointToPoint

* better initialization of variables

* Matrix4: added preMultiply method

* Matri4: preMultiply -> premultiply

* fix bug where gammaInput/gammaOutput were reset by the PMREM generators.

# Conflicts:
#	examples/js/pmrem/PMREMCubeUVPacker.js

* propagate encodings properly between PMREM CubeUVPacker and PMREMGenerator as well as through texture constructors.

# Conflicts:
#	examples/js/pmrem/PMREMCubeUVPacker.js

* turn off tonemapping, fix None HDR map option.

# Conflicts:
#	examples/webgl_materials_envmaps_hdr.html

* minor envmaps_hdr improvements.

# Conflicts:
#	examples/webgl_materials_envmaps_hdr.html

* fix double decode.

* recalc materials when changing texture encodings.

# Conflicts:
#	examples/webgl_materials_envmaps_hdr.html

* clean up envmap_hdr example.

Greater than or equal to readyState HAVE_CURRENT_DATA

Video texture should check ready state of video to see if current frame is renderable, not if future frames are renderable

That made phong_*vertex empty, so they have been removed.

an attempt at working around compiler errors mentioned here: https://github.com/mrdoob/three.js/issues/8161#issuecomment-200809856

Presumably, the previous version was correct.

FIxes #8432.

Raycasting with sprites is an approximation in that the sprite is treated as a disk. In addition, sprites can be non-square, and can be rotated.

With this change, if the sprite is square, the "clickable" region is inside the inscribed circle. If the sprite is non-square, the approximation is not very good, but it is better than before.

This commit removes the MAX_VERTEX_TEXTURE_IMAGE_UNITS === 0 code path.

Fix #8358