FIX: deprecated conversion from string constant to ‘char*’
     compiler: G++ 4.7.2 (flag: -Wwrite-strings)
FIX: as the global variable character_escape is now const,
     the variable esc is now const too (function print_string
     and print_binary_string).
     Indeed, the printer callback expectes to get a constant string.
remove useless option (we don't need the root privillege
Merge pull request #15 from NicolasDP/master

Minor fixes