Search for a byte in a string
#include <byte.h>
size_t byte_chr(const char *haystack,size_t len,char needle);
byte_chr returns the smallest integer i between 0 and len-1 inclusive such that one[i] equals needle.
If no such integer exists, byte_chr returns len.
byte_chr may read all bytes one[0], one[1], ..., one[len-1], even if not all the bytes are relevant to the answer.