Make list_wcwidth tail recursive.
Make json.skip_ws tail recursive.
Enable --exec-trace-tail-rec on some modules.

This avoids running out of stack space in debugging grades
even though the calls are self tail-recursive.
json: Compatibility with Mercury 11.07.

parsing_utils.next_char_no_progress missing.
tags: Compatibility with Mercury 11.07.

set.foldl2 missing.
text_entry: Compatibility with Mercury 11.07.

Changed argument orders in stack module.
README: Update allowable addressbook alias characters.
NEWS for 0.6 release.