Mark nscd service as forking in systemd service file (BZ #16639)

Currently the nscd service is installed in systemd as a simple
service, which means that it is able to handle its own errors and does
not quit.  Since nscd does not fit that description, i.e. it can exit
on errors like, say, failing to parse nscd.conf, it should be declared
as forking instead.
PowerPC: strncat optimization for PPC64

The optimization is achieved by following techniques:
1. Doubleword aligned memory access and compares using
   cmpb instruction.
2. Loop unrolling for byte load/store.
3. CPU pre-fetch to avoid cache miss.