xmlSplitQName2 returns NULL if the passed name does not have a prefix.  I understand from a newsgroup posting that this is the desired behavior.  However, the documentation says that it returns NULL if the passed name is not a QName.  Yet, a name without a prefix is still a QName, and the documentation even includes a grammar production for QName that shows this.  It would help to correct the documentation.

Perhaps:
Returns: NULL if not a QName or if there is no prefix.  Otherwise, the local part, and prefix is updated to get the Prefix.