convert to using .WAIT

clean up previous

fix race condition when building libcommon with make -j

add mkalias & revnetgroup

- build common/* once, into a library, rather than recompiling each of
the files multiple times in the other subdirectories (saves about
10% on compilation time)
- clean up the manual pages

A ypserv implementation, originally written by Mats O Jansson, with
some changes by me, including misc. cleanup, minor bug fixes, and
brand-new access control list code.