Have our own headers to declare the format of ONC (Sun) RPC messages on

Have our own headers to declare the format of ONC (Sun) RPC messages on
the wire; the definitions in many systems use u_long, which is 64 bits
long on many platforms - that's OK for in-memory structures, but it
doesn't match what's on the wire.  Use headers based on the Sun ones,
but use u_int32_t for fields, and otherwise make the structures match
what's on the wire, and change some names to avoid collision with
<rpc/rpc.h>, which print-sunrpc.c includes to declare "getrpcbynumber()"
and the structure it returns.

Record whether "getrpcbynumber()" is found, and use it only if it's
found, rather than basing the decisison on whether we're building for
Win32 or not.