Fix 9906: unaryFun and binaryFun should recognize static opCall

Structs or classes with static `opCall` should be recognized as valid
function objects.
Update ddocs.
Revert AA/array extension to unaryFun.

Per PR discussion.
Fix broken case of function object with non-static opCall.
Merge pull request #2556 from quickfur/issue9906

Fix 9906: extend unaryFun and binaryFun to recognize function objects