Add feet to drawmapscale

Author: Joshua Gardner

lib/mpl_toolkits/basemap/__init__.py

@@ -4491,6 +4491,8 @@ def drawmapscale(self,lon,lat,lon0,lat0,length,barstyle='simple',\
             length = length*1609.344
         elif units == 'nmi':
             length = length*1852
+        elif units == 'ft':
+            length = length*0.3048
         elif units != 'm':
             msg = "units must be 'm' (meters), 'km' (kilometers), "\
             "'mi' (miles) or 'nmi' (nautical miles)"