Clipping planes broken in IE

[ggetz]

See discussion in #6038.

There is an issue with the GLSL compilation in IE that disables clipping plane functionality.

[pjcozzi]

For example:

http://localhost:8080/Apps/Sandcastle/index.html?src=3D Tiles Clipping Planes.html&label=All

@likangning93 perhaps your infinite clipping planes and clipping boxes will fix this...

[pjcozzi]

Perhaps related to #6077

[pjcozzi]

@likangning93 as part of your infinite clipping plane and box work, we also want to fix this (post 1.41) - which I think will just happen by moving from uniform arrays to textures - but also by adding the infrastructure to Model.js so that shaders can be recompiled to add/remove the clipping plane code like Globe currently does.

@lilleyse can help once everything else is done for infinite clipping planes/boxes.

[likangning93]

Herm... not fixed yet, and also not working in Edge (although I don't think it's working in Edge in master either).

[likangning93]

Okay. This should be fixed in #6201, but the bug wasn't just uniform arrays. See https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/Shaders/Builtin/Functions/windowToEyeCoordinates.glsl#L34.

IE and Edge were always having this check (mat4 inequality) return false, which seems like a bug with their WebGL implementation.

[pjcozzi]

Good catch, thanks @likangning93

[mramato]

Removing priority next release, this will come in with #6201