List of special text property handling conditions for yanking.
Each element should have the form (PROP . FUN), where PROP is a
property symbol and FUN is a function. When the `yank' command
inserts text into the buffer, it scans the inserted text for
stretches of text that have `eq' values of the text property
PROP; for each such stretch of text, FUN is called with three
arguments: the property's value in that text, and the start and
end positions of the text.
This is done prior to removing the properties specified by
`yank-excluded-properties'.