Support for LongLong JSON reads (as Strings) to handle cases such as lar...

...ge integer IDs that are > 31bits in value (i.e.. Facebook User IDs)

NOTE: Code is direct from a Konrad Kiss implementation for DoubleDoodle in a branch of his there
the Longest 64bit long is 20 chars + 1 null terminator. KKs code originally had [21] but I like Pow2, so that's where 64 came from. Ammending to [32] and adding comment.