Allow changing the parameters for built-in post types

[scribu]

Currently, it's really hard to change a single aspect of the built-in post types.

As shown in 3:ticket:21943, users are reverting to all sorts of ugly workarounds.

What's needed is a filter for the args array, before any processing is done inside register_post_type().

[scribu]

21944.diff​ applies the 'post_type_args' filter right after the defaults are set.

[DrewAPicture]

​Relevant IRC discussion

[scribu]

To summarize, nacin pointed out that with the filter, devs could also mess with capabilities, menus etc. which would break things.

And allowing the filter for non-core post types is very niche, since plugins can just define their own filter, before calling register_post_type().

SergeyBiryukov: Related: #19590

[scribu]

See #21948

[MikeSchinkel]

This is a duplicate of #17447.