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The debug output was modified to output text strings using
single quotes instead of double quotes but the document missed
getting this update.

Create a LogContentTest class and move the functions to manipulate
a test to check on the log output there.  This will make it available
for other tests in the future.  As part of this bundle a bit more
work into the class to minimze the calls in the test routines.

Where reasonable remove extra copys of the values being pushed
onto the stack - instead of generating a copy just for the logging
simply use the value from the top of the stack directly.

Swtich to using single quotes around text values.

Added some more description in the classify document

This patch adds a set of log messages to indicate what values are
being popped from or pushed to the classification value stack.  This
is meant to be used by an administrator when debugging the expression
statements.