Unlike simple glyphs, which always have 'program' attribute (even when empty, with no instructions)
in composite glyphs, it's the presence of 'program' attribute that determines whether
the optional WE_HAVE_INSTRUCTIONS component flag is set or not.
Thus, the trim method (with remove_hinting=True) should delete the attribute for
composite glyphs.
Fixes https://github.com/fonttools/fonttools/issues/1550
* Implement glyf outline flags bit 6 when decompiling/compiling
* Add test data for outline flag bit 6
* Rename flags, use bitwise OR for setting flag bit
* Remove unneeded code
