add case for LTSpice executable filename

[ninja-lab]

I had to add

                    elif  os.path.exists(os.path.join(root,name,'XVIIx86.exe')):
                          cmd = os.path.join(root,name,'XVIIx86.exe')

in _find_LTSpice_wine() to get the installation to work. Otherwise it was throwing UnboundLocalError: local variable 'cmd' referenced before assignment