Fix fseeko/ftello/strcasecmp not being defined

[nightmareci]

Fixes building vendored SDL Mixer for me on Linux with wavpack enabled.

[madebr]

What do you think about this @sezero ?
I don't like how it handles _POSIX_C_SOURCE.

I also think this should be upstreamed. The project is very welcoming to external contributions.

[sezero]

I don't like how it handles _POSIX_C_SOURCE.

Neither do I.

What I don't understand is: wavpack builds just fine on linux by itself. Are compiler extensions disabled when wavpack is built under SDL_mixer?? I don't think so....

I also think this should be upstreamed. The project is very welcoming to external contributions.

I agree. We should see what upstream thinks.

[sezero]

What I don't understand is: wavpack builds just fine on linux by itself. Are compiler extensions disabled when wavpack is built under SDL_mixer?? I don't think so....

Maybe add an explicit set(CMAKE_C_EXTENSIONS ON) in wavpack cmake'ry ???

[madebr]

Maybe add an explicit set(CMAKE_C_EXTENSIONS ON) in wavpack cmake'ry ???

If that does it, then prefer to do set_property(TARGET wavpack PROPERTY C_EXTENSIONS ON) instead.

[sezero]

Maybe add an explicit set(CMAKE_C_EXTENSIONS ON) in wavpack cmake'ry ???

If that does it, then prefer to do set_property(TARGET wavpack PROPERTY C_EXTENSIONS ON) instead.

That would do too, I guess, provided that cli wavpack programs aren't affected by the issue.
(The If that does it still has emphasis though.)