osd: convert OSD font to OpenType

The old OSD font was a PostScript Type 1 font. Convert it to OpenType
to work around a fontconfig bug [1]. OpenType is a more modern format,
and the font file is quite a bit smaller, so this is actually a nice
change.

The conversion was done by opening the font with fontforge and saving
it as OpenType (CFF). fontforge showed a warning when doing this:

    The font contains errors.
      Self Intersecting
      Bad Private Dictionary

These seem to be harmless.

[1] https://bugs.freedesktop.org/show_bug.cgi?id=63922

Makefile

@@ -377,7 +377,7 @@ video/out/gl_video_shaders.h: TOOLS/file2string.pl video/out/gl_video_shaders.gl
 	./$^ >$@
 
 sub/osd_libass.c: sub/osd_font.h
-sub/osd_font.h: TOOLS/file2string.pl sub/osd_font.pfb
+sub/osd_font.h: TOOLS/file2string.pl sub/osd_font.otf
 	./$^ >$@
 
 # ./configure must be rerun if it changed