Create a fontset from an ASCII font FONT.
Optional 2nd arg RESOLVED-FONT is a resolved name of FONT.
If omitted, `x-resolve-font-name' is called to get the resolved name.
At this time, if FONT is not available, an error is signaled.
Optional 3rd arg FONTSET-NAME is a string to be used in
an appropriate name is generated automatically.
It returns a name of the created fontset.