parse_map_flags() silently truncates map flags after the first 't' or
'r'. This makes it accept arguments "true" and "revert". However, it
also breaks the perfectly sensible argument "ts", which should show
ships just like "st", but doesn't.
info bmap & friends document arguments "true" and "revert", and also
suggest flags 't' and 'r'. What a mess.
Make argument "revert" a special case. Deprecate flag 'r', and clean
up truncation there.
Don't truncate after flag 't'. If any bad flags follow, ignore
everything after 't', but deprecate that usage.
Drop .SY for map commands other than the one documented by the info
page.
Use the page's command to discuss arguments "revert" and "true", not
"bmap".
Clarify flags argument.
Modify nmap command to allow mapping around a nuke.
Add new command nbmap for bmapping around a nuke.
Add a new mapping flag 'n' for adding nukes to a map.
Correct syntax description for pmap, pbmap, lmap and lbmap
in player_coms[].
