Add help text for new option
@@ -396,6 +396,18 @@ ADVANCED COMPRESSION
-thorough : 1.25
-exhaustive : 10.00
+ -2planelimitfactor <factor>
+ Skip encodings with two weight planes, unless the best one
+ partition score using two weight planes is better than the
+ best one partition score using one weight plane by this
+ factor. Preset defaults are:
+
+ -fastest : 1.05
+ -fast : 1.05
+ -medium : 1.05
+ -thorough : 1.05
+ -exhaustive : 10.00
+
-2planelimitcorrelation <factor>
Stop compression after testing only one plane of weights, unless
the minimum color correlation factor between any pair of color
