New data type JSON_BSTRING for binary strings.

This string output type replaces all non printable bytes (00-07, 0b,
0e-1f, 7f-ff) to "\u00xx" sequences. This allows json decoders to
reconstruct binary string without interpreting binary sequences as
Unicode characters.
Merge pull request #13 from fln/master

New data type JSON_BSTRING for binary strings
avoid comparison between signed and unsigned
remove useless cast
fix 'unused parameter warning' by a reset of the printer
remove trailing white space
Merge pull request #14 from NicolasDP/master

Some minor fixes
check return value after printing
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
Merge branch 'master' of https://github.com/vincenthz/libjson