ACTION-2056: Coordinate the mappings for the various AAPIs of the enumerated aria-haspopup values

Rich, also modify the error section, especially the table that states what the fall-back mappings are for missing required aria-* attributes:
https://rawgit.com/w3c/aria/master/core-aam/core-aam.html#authorErrorDefaultValuesTable

The entire error section, for your reference:
https://rawgit.com/w3c/aria/master/core-aam/core-aam.html#document-handling_author-errors

Rich added all platforms but webkit for Mac. Joanie to do this part. Rich's branch was pulled in.

Rich's change merged with some editorial fixes:

https://github.com/w3c/aria/commit/673df28b8f80f3f415a1777a72a2ec2512927527

It's unlikely we need this change in 1.1 since the element that "has popup" already references the role type of the popup through the IDREF of @aria-controls or @aria-owns. For the sake of scoping, please reconsider whether this modification is critical for 1.1.

Of note is that this change is not backwards-compatible with ARIA 1.1 because authors changing aria-haspopup="true" to one of the new enumerated types will find that this breaks all current implementations. It will currently be treated as aria-haspopup="false" (the default value for ARIA 1.0).

The only implementation change that WebKit would require is to make the other token values (any string besides "false" or "undefined") exposed as the boolean True. It's unlikely any user-perceivable change would be required, since users are not used to hearing things like "popup button opens dialog" or whatever the intention was with this property.

@James, So, the problem with relationships is that if it has not been popped up yet it may not exist in the accessibility tree. So, the reason that the aria-haspopup valuse are present are to tell the user that the combobox will open a dialog, etc. so that when they land in new context they are not wondering why the web page author landed them in a dialog box from a combobox and hopefully they will not go back into having to retrace their steps to find out how they got there.

Closing as both AX API and UIA are not implementing this at this time. They may in the future. The mappings are given in the Core-aam.