remove libexpat dep (if possible)

[modeswitch]

Not sure if libexpat is really needed. Would be nice to remove it as a dependency if not.

[jonnor]

Any comment on this? What is libexpat used for in the codebase?

[modeswitch]

@jonnor I haven't had time to look into this, but the info is all in the repo if you would like to investigate.