inetd enhancements: move definitions to header file

[James Browning <jamesbrowning137%gmail.com@localhost>]

In implementing a key-value based syntax for inetd as progress on the inetd
Enhancements projet
(https://wiki.netbsd.org/projects/project/inetd-enhancements/), we have created
a number of new functions that rely on the servtab structure definition and some
other existing code. Should we create a separate header file to move the servtab
structure definition so we can move our new code into a separate C file, similar
to ipsec.c (but with a lot more code)? Otherwise we’ll probably just keep our
code and prototypes inside inetd.c.