more str/bytes fixes to read_values
more str/bytes fixes to read_values

git-svn-id: 9ab2475816adfb8420036182e3900ffc754382bd@386 516c0664-e049-0410-bc6e-8f9a6051a51d

pyvisa/pyvisa,hgrecco/pyvisa,rubund/debian-pyvisa,MatthieuDartiailh/pyvisa