Remove glsl-unit

[twpayne]

Unfortunately, the glsl-unit project (a GLSL minifier and templating system) seems to be dead. There are a number of outstanding bugs, the project has not been touched for a year and a half, and the original developer has moved on. The generated output is incompatible with IE11 (see #1051).

This PR adds a simple drop-in replacement for glsl-unit. It preserves the templating system (useful) and does simple minification, which works as well as GLSL unit for our simple shaders.

[twpayne]

Note that with this PR it's possible to remove the generated *shader.js files from the source tree, since they can be rebuilt with requiring the user to install glsl-unit. I propose to do this in a separate PR.

[elemoine]

Why not forking glsl-unit or writing a simple node-based tool replacement? It would be more inline with our will to use Node for the build system.

[twpayne]

Why not forking glsl-unit or writing a simple node-based tool replacement?

Modifying glsl-unit to fix the outstanding bugs requires a moderate understanding of compiler technology. glsl-unit doesn't even come with build instructions.

I'm not familiar with node, and we have a dependency on Python for gjslint anyway.

[fredj]

See also https://npmjs.org/package/glslmin
The project has not been touched for 10 months and I don't know if it fits our needs.

I'm +1 for the python replacement

[twpayne]

Thanks for the pointer to glslmin. It doesn't seem to support templating, and templating is useful to avoid having to write boilerplate code.

[elemoine]

I don't like that we have both package.json and requirements.txt. This really demonstrates that we're going in any direction for the build system. I hope to find time to rewrite this in js.

Please merge.

[twpayne]

I've updated the developer guide to mention requirements.txt.

[tschaub]

It looks like it should be possible to use glsl-unit with goog.node.FLAGS.consolidate_declarations set to OFF.

[tschaub]

This really demonstrates that we're going in any direction for the build system.

Agreed that the current lack of consensus on direction forward sucks.