NAME
        FindSegment - Finds a segment on the resident list (V36)

   SYNOPSIS
        segment = FindSegment(name, start, system)
        D0                     D1     D2     D3

        struct segment *findsegment(strptr, struct segment *, long)

   FUNCTION
        Finds a segment on the Dos resident list by name and type, starting
        at the segment AFTER 'start', or at the beginning if start is NULL.
        If system is zero, it will only return nodes with a seg_UC of 0
        or more.  It does NOT increment the seg_UC, and it does NOT do any
        locking of the list.  You must forbid() lock the list to use this
        call.

        To use an entry you have found, you must: if the seg_UC is 0 or more,
        increment it, and decrement it (under Forbid()!) when you're done
        the the seglist.

        The other values for seg_UC are:
                -1   - system module, such as a filesystem or shell
                -2   - resident shell command
                -999 - disabled internal command, ignore
        Negative values should never be modified.  All other negative
        values between 0 and -32767 are reserved to AmigaDos and should not
        be used.

   INPUTS
        name   - name of segment to find
        start  - segment to start the search after
        system - true for system segment, false for normal segments

   RESULT
        segment - the segment found or NULL

   SEE ALSO
        addsegment(), remsegment(), forbid()