An earlier change eliminated spaces between the close brackets of nested
template lists. Unfortunately that prevents the Windows debuggers from
matching some types to their corresponding visualizers (e.g., std::map).
This selects the SeparateTemplateClosers flag when generating COFF debug
info. Note that we were already making formatting adjustments under
similar circumstances for similar reasons.
This solves the immediate problem, but there aren't many tests for COFF
debug info (that I can see). I will be looking into integrated tests with
Dexter next.