[krbdev.mit.edu #2861] minor doc updates

[Ken Raeburn via RT]

Oops... I just checked in a couple minor doc updates that could stand
to go into the 1.4 release maybe, but I forgot to open tickets on
them...

* build.texinfo (The util Directory): Add the new support library.
(Installing the Binaries): Discuss parallel builds under GNU make.
* implementor.texinfo (Host Address Lookup): Document Mac OS X issues.

build.texinfo version 1.23
implementor.texinfo version 1.14