handling of DEL (0x7F) char in string parsing

[fulvioesposito]

As of RFC 4627 point 2.5, the unescaped allowed characters are 0x20-0x21 / 0x23-0x5B / 0x5D-0x10FFFF so 0x7F (DEL) is an allowed unescaped char.

In strings parsing, parson use iscntrl() to verify control characters. iscntrl() returns true even for 0x7F, yet it is an allowed character and should be accepted in unescaped form.

I posted a patch at https://gist.github.com/4270061

[kgabis]

Thanks for pointing this out, I applied your patch and pushed it to github.