Add new plot marker styles '|' and '_' (bug #61350) * NEWS: Announce addition. * gl-render.cc (make_marker_list): Add instructions for drawing '|' and '_' markers. * graphics.cc (radio_values::radio_values): Add special case in constructor from string of options to parse '|||' and return value '|'. * graphics.in.h (line, patch, scatter, surface): Add '|' and '_' to marker property for graphics objects which have this property. * __pltopt__.m: Add '|' and '_' to list of possible markers in input validation. * __gnuplot_draw_axes__.m: Add FIXME note about implementing these two markers in gnuplot. There doesn't seem to be an easy way to do this as it is not one of the defined point styles.

--- a/NEWS	Wed Oct 27 15:02:20 2021 -0400
+++ b/NEWS	Wed Oct 27 15:07:52 2021 -0700
@@ -129,6 +129,9 @@
 `"interpreter"` property and axes objects' `"ticklabelinterpreter"`.
 Type `doc "latex interpreter"` for further info.
 
+- The `"Marker"` property for plot objects now accepts `|` which draws
+a vertical line or `_` which draws a horizontal line.
+
 - The `FMT` format argument for plot commands now accepts long forms for
 color names which may be more understandable than the existing
 one-letter codes.  For example, the RGB value `[0 0 0]` can now be