36054447 Convert [namespace export -clear] interface to something less stupid.
Test suite does not demand the stupidity continue, thank goodness.
refinement
The flag TCL_LEAVE_ERR_MSG has no effect on the routine
TclGetNamespaceForQualName() so for goodness sake stop making any
special efforts to add it in when making calls.
added test
3605447 Make sure the -clear option to [namespace export] always clears,
whether or not new export patterns are specified.