Return a font name pattern for character CH in fontset NAME.
If NAME is t, find a pattern in the default fontset.
If NAME is nil, find a pattern in the fontset of the selected frame.
The value has the form (FAMILY . REGISTRY), where FAMILY is a font
family name and REGISTRY is a font registry name. This is actually
the first font name pattern for CH in the fontset or in the default
fontset.
If the 2nd optional arg ALL is non-nil, return a list of all font name
patterns.
(fn NAME CH &optional ALL)