A couple of definitions

[Joshua Lokken]

Hello

I am going through /etc/defaults/make.conf (4-stable) and am
at a loss concerning two items:  Objective C support, and 
libc_r (re-entrant version of libc).  What are those?  I built
the world recently without them, and I'm not witnessing any
problems, but I'm curious.  Google got me some answers
I couldn't understand...

Thanks in advance.
--
Best Regards,

Joshua Lokken