Merge pull request #77 from chipdude/master

use JSON_ALLOW_NUL with jansson load, as upstream just added it
double-converesion: add ARM 64 and OS X PPC compilation support (Florian Loitsch)
double-converesion: fix double-increment in Bignum::SubtractTimes; does not affect double-conversion from outside (Florian Loitsch)