bug#18077: 24.4.50; Info-quoted face should inherit default

[swiesner]

Currently, the `Info-quoted' face is defined as follows in info.el:

(defface Info-quoted
  '((t :family "courier"))
  "Face used for quoted elements.")

I do no think that mode faces should *hard-code* specific font families,
and thus bypass any customization of the default face that the user
might have made to pick their preferred font.

Besides, courier is not a particularly friendly choice.  There is no
specific font with that name.  The actual font depends on the font
configuration and aliasing picked by the OS and the user, and depending
on the quality of this configuration the appearance of this font varies
greatly.  If the configuration is particularly poor, or if a proper
substitute font is missing, Emacs might even fall back to X11 bitmap
fonts, which are particularly ugly on modern screens.

So just because it's pretty on your screen, it doesn't need to be pretty
on some else's screen.

Please remove the hard-coded font family and inherit from the default
face instead.