Expand Truetype instructions defined by IDEF[]

In the process of extracting hint instructions in xgridfit format,
ttx from the current (2.4) fonttools can't disassemble those user
defined instructions.

Only Serif and Serif-Bold (NanumMyeongjo) have them.
Embed hinting written in xgridfit
Add the first hinting for backslash

Sans-Bold hinting is not enough. It does not count for roundings which
need more study for proper hinting.