Add M_CANAL flag to indicate which ships can navigate a canal
in a big city. Remove the hard code values for canal from
shp_nav_one_sector() for which ships can navigate a canal.
Set M_CANAL flag in ship_chr_flags[] to match the hard
coding in shp_nav_one_sector().
Update Ship-types.t with new canal flag.
Update Sector-types.t to indicate that cities have canals.
Useless, remove. Users changed to check mchr's sentinel, because
that's clearer than comparing the index to N_MAXSHIPS or sizeof(mchr)
/ sizeof(*mchr).
(mchr): Change sentinel's m_name to NULL.
be skipped or stored in arrays of size I_MAX. I_NONE's int equivalent
becomes -1 by this patch, so all array indices of type i_type have been
checked not to use I_NONE as index. This change reduces the size of the
arrays stored in files.
capacities to straight arrays. Users now subscript the array instead
of calling vl_find() or walking the variable data structure.
(mchr, lchr): Initializers adapted.
(vl_find): No longer used. Remove file.
