AIX 4.3 needs NM_FOR_TARGET as well

[David Edelsohn]

	Sigh.  The multilib libraries in gcc subdirectory did not need
NM_FOR_TARGET and that was not defined in gcc/Makefile.in but the
top-level libraries do (when building _G_config.h).  I have committed that
change to the mainline sources and it will need to be included in a minor
release if not this first release.  Do we have a known bugs location yet?

David