Fix Haiku detection in webkitdirs.

No need to force --haiku on the command line anymore.
Fix crash when using media controls.

One of the required js files was not being loaded, leading to the JS
interpreter not finding a variable. This was made difficult to debug by
a crash preventing the usual console message from being shown.
Remember last used directory for upload filepanel.

Fixes #10961.
Avoid useless linking of ffmpeg and opengl.

Until we actually implement webaudio and webgl, at least.