[objc] RFC: Move the ChangeLog objc/* entries to objc/ChangeLog

[David Ayers]

Hello,

I don't have a set opinion on this, but I've been following the changes 
of the objc-improvements-branch and I'd just like to point out that this 
branch splits up the C-based frontend files in a modular form so that 
they can be recombined for a concrete frontend.  I like the approach.  
My point is that this should be considered when deciding on how to 
potentially reorganize the ChangeLogs in general, as a change in one 
file may or may not affect multiple concrete frontends.

Cheers,
David