Fixed severe bug in PSOCK_READTO (?)

Either I found and fixed a severe bug in PSOCK_READTO() or I misunderstood something completely. To me PSOCK_READTO() is supposed to return if either the supplied character was read or if the user supplied buffer is exhausted - sor far so good.

However if the latter occurs up to now PSOCK_READTO() was continuing to process characters already read from the network (aka present in the uIP buffer) in order to check if the supplied character was found there and adjust the return value accordingly. But this means that the character processed this way were lost forever for the caller as the next call to PSOCK_READTO() would continue to read past the characters processed this way.

Therefore I removed that character processing altogether. So now if the user supplied buffer is exhausted before the supplied character is found the next call to PSOCK_READTO() starts exactly where previous call left off.