added function to find the length of a hexstring when converted to ascii; amended a type signature
use memcpy instead of strncpy and custom counting function instead of strlen, because i realized that string assumptions (\0 nowhere but the end) do not hold with the xor'd bytes
forgot exit on utility_file_error(const char*) and added newlines to the end of the fprintf calls so they won't be stuck in the buffer
remember, nothing in c is initialized by default. stuff from malloc is not zero'd out. changed malloc -> calloc, thus fixed a bug in utility_hex_to_ascii
completely changed heuristics to identify english test, works for all the test cases now.