ISSUE-435/ACTION-1532/ACTION-1530  Mapping for role="text".

Added MSAA+UIA Express, UIA, and ATK/AT-SPI mapping for the new
"text" role.
ISSUE-568/ACTION-1540, 1538, 1539: Mappings for aria-modal.

Added mappings for aria-modal="true"/"false" for MSAA+UIA Express,
MSAA+IA2, UIA, and ATK/AT-SPI.
Updated "Change Log" section.

Noted substantive changes since publication of last WD.
Added link to "Events" section.

Put a link into section 5.8.1 "State and Property Change Events"
that points to section 5 "Name and Description Change Events" of
the name computation document.