Support the COLUMNS environment variable for help/usage output

man/rgbasm.1

@@ -177,6 +177,9 @@ or
 The defaults are 0123.
 .It Fl h , Fl \-help
 Print help text for the program and exit.
+(Help text wraps to the value of the
+.Dv COLUMNS
+environment variable if that is defined as nonzero; or else to the console window width if output is to a TTY.)
 .It Fl I Ar path , Fl \-include Ar path
 Add a new
 .Dq include path ;