[lltx] mkluatexfontdb & Mac OS X

[Arthur Reutenauer]

	Hello,

> luaotfload | loading font: /usr/X11R6/lib/X11/fonts/OTF/SyrCOMUrhoyBold.otf
> Bus error

  I can't reproduce the problem, and I have that font, as well as all
the other Meltho fonts.

> luaotfload ø loading font: /Library/Fonts/NISC18030.ttf./otfl-font-nms.lua:255: bad argument #1 to 'close' (fontloader.splinefont expected, got nil)

  I confirm the problem here: this is a simplified Chinese font that
contains only bitmaps; its internal structure seems very weird to me,
there is no 'glyf' table (I'm not sure if that's even conformant to the
standard!).  We can safely ignore it, your fix handles this case nicely.

> luaotfload | loading font: /Library/Fonts/华文楷体.ttf
> Bus error

  Can't reproduce either, and I have the font (its name reads "Huawen
kaiti", by the way, it's simplified Chinese font in Kai style).

	Arthur