properly markup <$> in documentation of alterF

[Flupp]

For both IntMap variants, the < and > did not appear in the haddock output.

While at it, also in the documentation for the other alterF variants the <$> was turned into a hyperlink.

[meooow25]

Hi, thanks for fixing the bad Haddocks for IntMap.

While at it, also in the documentation for the other alterF variants the <$> was turned into a hyperlink.

I would prefer it if we did not do this, because the link is a bit distracting when it is not the focus of the documentation. Do you mind reverting those?

[Flupp]

I thought it made the markup more uniform and might also be helpful for beginners.

Anyways, I now just added escaping where needed.

I also rebased on current master.

[meooow25]

Great, thanks!