include <istream> and <ostream> in spell.hpp to enable compile

[clort81]

from conversation in IRC, include and in spell.hpp to enable compile on linux

[Celtic Minstrel]

I think <iosfwd> should be sufficient instead of <istream> and <ostream>, does that work?

[Nat Quayle Nelson]

I can compile on Linux (Arch). Was this fixed? If we can get Linux CI working, I think we can close this.

[Celtic Minstrel]

Linux CI is now working so yeah, I guess there's no reason for it to stay open.

For what it's worth, the Linux CI is building on Ubuntu.