[WWcvs] pg: Add mg as a mass unit.

[Gavin L. v. a. <we...@ma...>]

Log Message:
-----------
Add mg as a mass unit.  Hopefully the fact that this wasn't here before
is an oddity rather than indicating that I'm screwing something up.

Modified Files:
--------------
    pg/lib:
        Units.pm

Revision Data
-------------
Index: Units.pm
===================================================================
RCS file: /webwork/cvs/system/pg/lib/Units.pm,v
retrieving revision 1.6
retrieving revision 1.7
diff -Llib/Units.pm -Llib/Units.pm -u -r1.6 -r1.7
--- lib/Units.pm
+++ lib/Units.pm
@@ -214,12 +214,17 @@
                            's'         => -1
                           },
 # MASS
+# mg   -- miligrams
 # g    -- grams
 # kg   -- kilograms
 #
+                  'mg'  => {
+                           'factor'    => 0.000001,
+                           'kg'        => 1
+                          },
                   'g'  => {
                            'factor'    => 0.001,
-                           'kg'         => 1
+                           'kg'        => 1
                           },
 # ENGLISH MASS
 # slug -- slug