* MAINTAINERS: Mark a29k target as obsolete.

* MAINTAINERS: Mark a29k target as obsolete.
* Makefile.in (a29k-tdep.o, remote-adapt.o, remote-eb.o)
(remote-mm.o, remote-udi.o): Obsolete.  Remove references in
comments.
* NEWS: Note that a29k targets are obsolete.
* a29k-tdep.c: Mark as obsolete.
* configure.tgt: Mark a29k-*-aout*, a29k-*-coff*, a29k-*-elf*,
a29k-*-ebmon*, a29k-*-kern*, a29k-*-none*, a29k-*-udi* and
a29k-*-vxworks* targets as obsolete.
* remote-adapt.c: Obsolete.
* remote-eb.c: Obsolete.
* remote-mm.c: Obsolete.
* remote-udi.c: Obsolete.
* config/a29k/a29k-udi.mt: Obsolete.
* config/a29k/a29k.mt: Obsolete.
* config/a29k/tm-a29k.h: Obsolete.
* config/a29k/tm-vx29k.h: Obsolete.
* config/a29k/vx29k.mt: Obsolete.