Provide glew stubs

[behdad]

Many apps use glew as a GL portability layer. Glew is a header-only library that #define's all GL (and extension) symbols to go through an indirection layer. Emscripten can provide glew headers that would obviate the need to disable glew usage in application code.

In short, just copy glew.h, glxew.h, and wglew.h, remove the lines that #define all symbols, and adjust extension mechanism to fit webgl, or if webgl does not provide extension API, just define them appropriately.

[azmeuk]

Here is an interesting bug at GLEW's source forge: https://sourceforge.net/p/glew/bugs/207/

[marcosscriven]

Would just like to +1 this - trying to refactor OpenCSG to remove dependency on GLEW results in a bit of a mess.

[Cloudef]

I've done some work on this, see #1878. It's not perfect, but it's good enough to get software running. The most cleanest way would to have emscripten compatibility at upstream, since glew headers are generated from the build system.

[stale]

This issue has been automatically marked as stale because there has been no activity in the past 2 years. It will be closed automatically if no further activity occurs in the next 7 days. Feel free to re-open at any time if this issue is still relevant.