documentation does not mention fp_read_unsigned_bin

[rofl0r]

imo everybody intending to do any real-life work with tomsfastmath will require this function to import his binary private keys etc. it should be mentioned right after fp_init() and fp_set(). i spent about half an hour to search for this functionality in both tfm pdf and ltm pdf without success, and only found out by digging through the ltc rsa code.