osd: osd_font.h -> osd_font.pfb
Add osd_font.pfb, which is the actual font file that was previously
stored in osd_font.h. Use file2string.py to turn it back into a header
during the build process.
Fix file2string.py to work with the font file. The script was written
to be able to deal with binary files, but it had a bug corrupting some
data: e.g. the byte sequence 0x1 0x37 was printed as "\17" (0x1 was
escaped as "\1", and 0x37 was kept as a literal "7"), which would be
interpreted as the single character 0xF. Always pad octal literals to
length 3, which makes the escape sequences unambiguous.