Include alext.h header for AL

[gabeklavans]

The docs claim support for some OpenAL extensions, however I was a bit confused to find the alext.h missing when trying to utilize the ALC_HRTF_SOFT extension. Based on this test, it looks as if the define value must be used directly in order to use the extension, which is a little difficult to figure out, to me.

Is there a reason to not add the alext.h file found in the openal-soft include folder to the "emscripten/system/include/AL" folder? I believe this would also alleviate issues like #9851 and would render #9852 obsolete.

As of writing I see that the discussion in #9852 suggests doing exactly this, but I figured I'd make this issue just to make the potential solution even clearer for anyone willing to revive the effort to remedy this (I may do so myself, if I find the time)

[sbc100]

Sounds like it would be a good idea to add that header. It may also take some implementation work to make those extensions work. Would you be interesting in working on this and sending a PR?

[gabeklavans]

Yeah I'm definitely interested in making a PR to bring in the header

It may also take some implementation work to make those extensions work.

By "those" do you mean the ones currently supported by emscripten? Or all the extensions available in the header (that would be possible to implement in emscripten)?

[sbc100]

I would imagine that the extensions could be probed for at runtime? So you wouldn't need to make them all work, just the ones that we report as working. having said that I know almost nothing about this API so that it might not work that way :)

[gabeklavans]

I would imagine that the extensions could be probed for at runtime?

Yes, openal-soft provides a function to check if an extension is available at runtime. However, I also don't know how it works haha. I'll look into to it when I start on the PR