[PLEASE TEST] getserv* nsswitch patch

Hello!
I think the best way to solve the problems with getserv* functions is to
implement them via nsdispatch. It gives an ability to plug in any
appropriate functionality later.
I've attached the patch to libc, which does it (It should be applied to 
files in src/lib/libc/net) It implements nis, files and compat sources. 
Any other source can be plugged dynamically as nsswitch module. 
Later I can implement any other pluggable module. 
Besides, there is a lookupd, which can be plugged into the 
nsswitch system too.

Thanks,
Michael