& btmapunits()
  
  Syntax: btmapunits(<MapOBJ>,[<x>,<y>,<z>,<range>])
 
  This function returns a space delimited list of the dbrefs of 
  objects of XTYPE:MECH on <MapOBJ>.
 
  Arguments:
  There are 3 valid forms:
 
  * btmapunits(<MapOBJ>) - lists all appropriate units on the map
  * btmapunits(<MapOBJ>,<x>,<y>,<range>) - lists all appropriate 
    units within <range> of <x>, <y>
  * btmapunits(<MapOBJ>,<x>,<y>,<z>,<range>) - lists all appropriate 
    units within <range> of <x>,<y>,<z> 
 
	Note: The function does not take the altitude of a unit into 
	consideration when ascertaining if it is within range UNLESS the 
	third form is used (ie the <z> argument is included)
 
  Continued in btmapunits()2