Merge the implementations of pp_e{host,net,proto,serv}ent.

Merge the implementations of pp_e{host,net,proto,serv}ent.

PL_op_desc[] rather than PL_op_name(), as the OPs are internally named e*ent,
but implement the ent*ent functions, and when unimplemented report themselves
using the function name. No need for OP_DESC(), as the switch statement means
that we can't encounter OP_CUSTOM.