* tracing in the "u" mode now works
* trace_vdelete() with wrong mode no longer break tracing
* trace_vinfo() now always returns a list of pairs of strings
window is created for every test class.
Fixed Tkinter images copying operations in NoDefaultRoot mode.
Tcl command names generated for "after" callbacks now contains a name of
original function.
Tkinter.Variables; harmonize exceptions to ValueError; only delete variables
that have not been deleted; assert that variable names are strings
Patch by Andrew Svetlov.
