Updated WOFF2 spec is available for review

Folks,

Per action 194 I made the following changes in the WOFF2 spec [1]:

-          Handling of the empty glyph records in glyph table transform: instead of requiring a decoder to create an empty glyph record with no contours and zeroed-out bbox we should rather handle this by simply omitting the glyph record and creating a new entry in the loca table with the offset pointing to the previously created [last] glyph record so that loca[n] = loca[n-1];

-          Added new conformance case for AT [2]: mustClearEmptyBBox - needs test description!

-          Eliminated the DC conformance case mustCalculateEmptyBBox;

-          Changed UA [3] conformance case mustRejectNonEmptyBBox - now set to unconditionally reject a font that has explicitly encoded bbox of an empty glyph. The existing test description seem to be fine, needs review!

-          Special case handling for empty glyph records in hmtx transform (action 194): in order to confirm hmtx transform eligibility check that lsb of an empty glyph is equal to zero.

Let's review and discuss it tomorrow during our telcon.

Thank you,
Vlad

[1] http://dev.w3.org/webfonts/WOFF2/spec/
[2] https://www.w3.org/Fonts/WG/wiki/TestPlan20-AuthoringTool#Testable_Assertions
[3] https://www.w3.org/Fonts/WG/wiki/TestPlan20-UserAgent#mustRejectNonEmptyBBox