performance improvements: replace memcmp

performance improvements: replace memcmp

 - looping forward while moving a pointer and doing memcmp isn't fast. replace it by strstr
 - \r\n can be done in a pointer dereferencing comparison.

Note: maybe we need to fallback to the memcmp way if there is binary content?
In that case we should do a little smarter and try to use contentlength-headers etc.