Iterates through a tag list, skipping and chaining as dictated by system tags. TAG_SKIP will cause it to skip the entry and a number of following tags as specified in ti_Data. TAG_IGNORE ignores that single entry, and TAG_MORE has a pointer to another array of tags (and terminates the current array!). TAG_DONE also terminates the current array. Each call returns either the next tagitem you should examine, or NULL when the end of the list has been reached.
INPUTS
tagItemPtr
doubly-indirect reference to a TagItem structure. The pointer will be changed to keep track of the iteration.
RESULT
nextTag
each TagItem in the array or chain of arrays that should be processed according to system tag values defined in utility/tagitem.h) is returned in turn with successive calls.