Function:
char *
NetGetClientHostname(Client *c, char *hname, int maxhostlen)
Given a buffer hanme and the size of that buffer, maxhostlen,
puts the hostname of the remote client into the buffer.
Usually, the client's hostname will will be available through
GetClientHname() if GetClientMaxHlen() returns non-zero on the
client. If however, you have defined GetClientMaxHlen() to return
zero, GetClientHostname() is the function to call, since the
data will not be available through GetClientHname().
Returns a pointer to the buffer on success, or NULL on error.