TypeId.isLongConcatableTypeId() should not return true for XML data type.

Since XML is not a type that can be concatenated this method should return false.
I see from the comments that it was set this way to take advantage of existing code that disallowed such a type being used in certain situations. However such overloading leads to confusion and the potential of bugs, much cleaner& easier to understand to have explict use of isXMLTypeId() when checking for XML types.