[oleaut32] implement VarMod() + tests, fix bug in VarNot()

* dlls/oleaut32/variant.c Chris Morgan <cmorgan(a)alum.wpi.edu> Implement VarMod(). Fix VarParseNumFromStr() to work correctly with NUMPRS_HEX_OCT flag. Add a few trace outputs. Fix VarNot() with VT_CY. * dlls/oleaut32/tests/vartest.c Chris Morgan <cmorgan(a)alum.wpi.edu> Implement tests for VarMod(). Added char *vtstr() to enhance test debugging by returning a text string that corresponds to the inputted type. Still have a couple of issues with this change. I'm not sure why the (BSTR) tests fail under wine and not windows, I've wrappered them with todo_wine{} but they still get listed as failures. I'm not sure if the fix to VarParseNumFromStr() is the most correct. It does appear to be exactly what windows does, overwrite the characters in the buffer but lie and return an incorrect character count. Also, testing the types in VarMod() results in some 700k additional tests and adds some time to the tests, something like 6 seconds on my machine. Is this simply too much to test? It certainly helped me nail down the types for VarMod(). Thanks, Chris