lynx版本的strstr实现

char *strstr(const char *haystack, const char *needle)
{
    register char *p = NULL;
    register char *q = NULL;

    if(!*needle)
         return (char *)haystack;

    while(*haystack)
    {
        p = (char *)haystack;
        q = (char *)needle;
        do{
            if(*q) return (char *)haystack;
        }while(*p++ == *q++)
        haystack += 1;
    }
    return 0;
}