drop_item_A: Fix increment of HL.
Note some suspicions about player numbers.
plot_bitmap: Sort argument list.
Document all message queue variables.
Document saved_* vars to be a 'pos' (x,y,vo) structure.
Document map_position.
Document searchlight_state.
Document items_held.
Document character_index.
dispatch_table_thing -> dispatch_timed_event,
dispatch_counter -> clock,
user_locked_out_until -> player_locked_out_until.
wire_snipped -> snipping_wire.
tile_refs_for_statics -> static_graphic_defs.
Document return conditions of user_confirm.
Fix shovel_key_mask -> shovelkey_mask.
screenlocstrings -> escape_strings.

+ Document have_required_items, item_to_bitmask.
Expand out twentyonelong.
Use vischar_BYTE1 flags for the contents of $8001.
Fix incorrect var references.
byte_CDAA: Document suspicion about this being transitions.
is_item_discoverable: Drop comment question now answered.