tolerant of dangling pointers from objects
that are exactly traced.  Profiling is one tool we can use to find
sites that use explicit deletion.  (Another tool is making GC::Free
private, which will trigger compilation errors in client code that
calls it.)


<h2> Basic operation </h2>

<P> The profilers both work the same way.

<UL>

<LI><P> First we require MMGC_MEMORY_PROFILING to be enabled.  That's
controlled by AVMFEATURE_MEMORY_PROFILER; in shell builds it is
enabled in DEBUGGER builds but can otherwis