Documentation: panels nowadays can display more than 2 columns.

In the past panels supported up to 2 "columns" only. We update the
documentation.

Note: a naive fix is to change it to say "After the panel size, you may specify
the number of columns to display in the panel". Unfortunately, users may think
by "columns" we mean "fields", so we have to word it differrently.

Signed-off-by: Mooffie <mooffie@gmail.com>

doc/man/mc.1.in

@@ -840,9 +840,10 @@ The user display format must start with a panel size specifier.  This
 may be "half" or "full", and they specify a half screen panel and a
 full screen panel respectively.
 .PP
-After the panel size, you may specify the two columns mode on the
-panel, this is done by adding the number "2" to the user format
-string.
+After the panel size, you may specify how many listings to fit in the
+panel, side\-by\-side (in other words: how many times to repeat the
+fields horizontally). This defaults to 1. You may change this by adding a
+number from 1 to 9 to the format string.
 .PP
 After this you add the name of the fields with an optional size
 specifier.  This are the available fields you may display: