I'd like to add support for 'outline-minor-mode' in Eshell. However, 
Eshell's use of field properties confuses outline.el. Attached is a WIP 
patch + demo code for Eshell that should resolve this.

The main issue was that outline.el uses 'line-beginning-position' and 
friends, which respects field boundaries, but I think we want to avoid 
that for 'outline-minor-mode'. Maybe we could use 'pos-bol' and friends 
instead, but my understanding is that 'line-beginning-position' respects 
display directionality (which we probably want), but 'pos-bol' doesn't.

You can try things out here by starting Eshell and activating 
'outline-minor-mode'. You can also see the problems by applying only the 
Eshell part of the patch.

Any thoughts? Is this the right way to go about this? (Note: I think the 
Eshell side of things will take more work, which I'll address in a later 
bug. However, this should be enough to show off the problems on the 
outline.el side.)