Added -no_empty switch to export_vars. If specified, variables with an empty string value will be suppressed from being exported. This avoids cluttering up the URLs with lots of unnecessary variables. If we weren't this close to an important release, I would advocate making -no_empty the default behavior.
In order to get Logger Tcl API tests to pass on 4.6 branch I had to add the new procs util_sets_equal_p and aa_run_with_teardown (previously added on cvs head)