& btmapemit()
    
  Error Messages:
 
  * If <MapDB> is not valid the function returns #-1 INVALID MAP
  * If <message> is not valid (eg a null string) the function returns 
    #-1 INVALID MESSAGE 
 
  Example:
  Given that #62 is a valid mapobject
 
  > think btmapemit(#62, Fascinating Message)
  1
 
  The occupant(s) of any units on the map will see:
 
  Fascinating Message
