[Fontconfig] How to ignore OpenType Collection fonts

[Masamichi Hosoda]

>> In the near future, if the number of available OTC fonts are grown,
>> this way will become unusable.
> 
> Why it is important for you to ignore OTC fonts specifically?

LilyPond uses fontconfig for finding fonts.
However, LilyPond could not support OTC fonts.
If you use LilyPond with an OTC font, it raises an error.
In order to avoid the error and find other fonts,
it is necessary that OTC fonts are ignored.

In addition, ghostscript can not handle OTC fonts.

Current LilyPond has added limited OTC support.
Soon, LilyPond will be added more complete OTC support.
However, it is still limited and ignoring OTC fonts are necessary.