#89 Add guidance for incomplete letters/signs

[BODARD Gabriel]

As requested by Christian Prager on Markup ( http://lsv.uky.edu/scripts/wa.exe?A2=ind1501&L=markup&D=1&O=D&X=7C0AF26B279219B3FE&P=808 ). He's interested in marking up incomplete or damaged logographic characters, for which it's important to say more than simply "underdotted". This is occasionally a desideratum for Greek/Latin as well, but we've never had a decent recommendation for this other than, "Use SVG"!

[BODARD Gabriel]

Will email Christian asking for more clarification.

[Elli Mylonas]

See also this discussion: http://lsv.uky.edu/scripts/wa.exe?A2=ind1606&L=markup&D=1&O=D&F=&S=&P=1718

[BODARD Gabriel]

This ticket should be merged with the discussion on [features:#110], and the Mayan and Sankrit problems discussed together with a view to a more generic solution (even if unique features are needed for both projects).

[BODARD Gabriel]

Merged with [#110] and closed.