Matplot_properties: the "tag" property is not documented
@sgougeon)
Reported by Samuel GOUGEON (BUG DESCRIPTION:
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The "tag" attribute is available for the Matplot entities.
It is well readable, writable and displayed, but it is not documented:
Scilab 5.5.2: https://help.scilab.org/docs/5.5.2/en_US/Matplot_properties.html
Scilab 6.0b2: https://help.scilab.org/docs/6.0.0/fr_FR/Matplot_properties.html