bug#32210: Support medium weighted fonts

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: carlosjosepita@gmail.com,  32210@debbugs.gnu.org
> Date: Mon, 18 Nov 2019 11:41:42 +0100
> 
> I chose "Ubuntu Regular" and "Ubuntu Medium":
> 
> Weight: 400, symbol normal
> Weight: 500, symbol semi-bold
> 
> And: Added wrinkle: In Emacs, the "Regular" font is heavier than the
> "Medium" font (but they're not in the Gtk selector).

Sorry, I don't understand: is this "wrinkle" due to the font, or is
this something Emacs does?  If the latter, can you point out where we
treat "regular" heavier than "medium"?