Extend the description for ESRCH a bit.
Extend the description for ESRCH a bit.

This errno can also be returned if the passed process identifier doesn't
correspond with a process group.

Discussed on:	arch@
MFC after:	1 week

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase