Before this change, feaLib would sort coverage tables by glyph name,
which is against the OpenType specification. The current unittests
happen to use only glyphs where the ordering is identical whether
sorting by name or by ID; but I am about to add unittests (for GPOS)
where the ordering is different.
The ordering cannot be enforced by otTables because otTables does
not have access to the font's glyph order; therefore, the sorting
needs to happen inside feaLib.
Generated by running example 1 from the Feature File specification
section 5.f.i (Specifying a Chain Sub rule and marking sub-runs)
through AFDKO's makeotf tool, and then decompiling the resulting
GSUB table with ttx.
The actual test is commented out because the current version of feaLib
is not able to produce this output yet; marked with a TODO comment.
Currently, the compiler uses them to figure out which set of
languagesystems would apply for the current scope. However, this
information is not yet used for anything.
