[glade] Gtk plugin: add 3 missing displayable value for GtkCellRendererText::underline

[Juan Pablo Ugarte <jpu src gnome org>]

commit 0d37352f28eaa491cf8cdffe2f81781fee4f96e0
Author: Juan Pablo Ugarte <juanpablougarte gmail com>
Date:   Mon Aug 17 19:26:16 2020 -0300

    Gtk plugin: add 3 missing displayable value for GtkCellRendererText::underline

 plugins/gtk+/gtk+.xml | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/plugins/gtk+/gtk+.xml b/plugins/gtk+/gtk+.xml
index 8551e3f7..2f7f9993 100644
--- a/plugins/gtk+/gtk+.xml
+++ b/plugins/gtk+/gtk+.xml
@@ -4731,6 +4731,12 @@
               <value id="PANGO_UNDERLINE_LOW" name="Low"/>
               <!-- PangoUnderline enumeration value -->
               <value id="PANGO_UNDERLINE_ERROR" name="Error"/>
+              <!-- PangoUnderline enumeration value -->
+              <value id="PANGO_UNDERLINE_SINGLE_LINE" name="Error"/>
+              <!-- PangoUnderline enumeration value -->
+              <value id="PANGO_UNDERLINE_DOUBLE_LINE" name="Error"/>
+              <!-- PangoUnderline enumeration value -->
+              <value id="PANGO_UNDERLINE_ERROR_LINE" name="Error"/>
             </displayable-values>
           </property>
           <property id="attr-underline" name="Underline column" save="False" default="-1" 
custom-layout="True">