WOFF2 spec changes

Folks,

I made the following changes (http://dev.w3.org/webfonts/WOFF2/spec/):
Action 188: allow null transform for glyf and loca

-          Table directory description was updated to say that the flags value (bit 6 and 7) need to be relied on in determining whether the a modifying transform was applied, and consult the combination of the table tag / transform version number to determine the specifics;

-          Description of the flags bits 6 and 7 was updated to add null transform for glyf and loca tables (transform version 3);

-          Removed explicit references to transformed table tags in table directory to make it open for future extensions;

-          Added references to null transform in sections 5.1 (glyf) and 5.3 (loca) transform descriptions. In addition, the loca table transform is now defined as "conditional mandatory", i.e. it is mandatory if glyf table is transformed but both tables can be presented in their original shape with null transform. There is an additional FF conformance statement conform-transformedLocaMustAccompanyGlyf that needs a new test be defined;
Action 189: hmtx transform description

-          Edited the transform description to make it font collections friendly (removed "file" in reference to individual font and added language to define the encoder behavior when the input file is a font collection;
Action 190

-          Added two new AT conformance requirements conform-mustCheckLSBAllGlyfTables and conform-mustNotApplyLSBTransformForOTC to  account for this change - need new test descriptions;

-          Open issue - a new FF test was suggested to cover the invalidly created hmtx transform but I don't think we can make it testable; in order to determine whether the hmtx transform was applied properly we need to reconstruct the glyph table first which is not in scope for FF validation, DC test seems to be more appropriate for it but it gets a lot more complicated. Comments?

Thank you,
Vlad