This procedure converts a string into a <inet-addr>
.
If the first character of the string is a digit, then
the string is interpreted as a dotted IP address
(e.g., 204.71.200.72). Otherwise, it is interpreted
as a host name and resolved using gethostbyname.
If the host name cannot be found, or it has no address, or
if the resolver library encounters some other error, a
<resolver-error>
condition is signalled.