New face homoglyph

New face homoglyph

Suggested by Eli Zaretskii, from a feature request by
Alan Mackenzie (Bug#24468).
* doc/emacs/display.texi (Standard Faces, Text Display):
* etc/NEWS: Document this.
* etc/themes/dichromacy-theme.el, etc/themes/leuven-theme.el:
* etc/themes/light-blue-theme.el, etc/themes/manoj-dark-theme.el:
* etc/themes/tango-dark-theme.el, etc/themes/tango-theme.el:
* etc/themes/wombat-theme.el:
Customize homoglyph to be the same as escape-glyph.
* lisp/cus-theme.el (custom-theme--listed-faces):
Add homoglyph.
* lisp/faces.el (homoglyph): New face.
* lisp/startup.el (startup--setup-quote-display): Use it.