Patch to MAINTAINERS

[DJ Delorie]

> Some OS port maintainers were listed in the general section in
> maintainers, and one target maintainer - for a removed target so now
> effectively write-after-approval - was also listed in that section.
> This patch moves them to the appropriate sections.  Applied to
> mainline.

Hmmm... DJGPP is both an OS and a target (I think it's cross built
more than natived these days), not that I care where my entry goes ;-)