Allow child theme authors to override /_inc/ajax.php

[r-a-y]

Contrary to ​the comments in /_inc/ajax.php, it is currently not possible to override ajax.php in your child theme.

The attached patch fixes this, however I wouldn't recommend the general practice of overriding ajax.php as there's too much functionality built into bp-default; I'd just pick and choose the actions I'd want to override instead.

I'll leave it to the core devs to decide whether this should be included or not.

[DJPaul]

You'd need to check if the file existed, as it might not be in most child themes. I'm not sure if a file_exists or a apply_filters would be most appropriate here.

[r-a-y]

Yeah, maybe just remove the comment in ajax.php about overriding.

[r-a-y]

Removes comment about overriding ajax.php in child theme; remove trailing whitespace

[djpaul]

(In [4354]) Remove misleading documentation from _inc/ajax.php. Fixes #3156, props r-a-y