hgview #105330 Implement $ hgview --version [done]

Having a --version option is pretty much standard theses days. It would be nice to have that in hgview too.

prioritynormal
typeenhancement
done in<not specified>
load left0.000
closed by#f1ef01d91b39 [option] add a version option (closes #259595, #259572, #105330, #7316)