Two OSX fixes

- When echo=True, the full output is not received in this condition,
  strangely enough, its a buffer of exactly 1024, any more than that,
  no more bytes are received in the expect/select loop, even when
  specifying very large values of searchwindowsize= and maxread=.
  There is no reason for echo=True, we only rewrote the tests for
  echo output to debug unexpected travis-CI behaviour, which we
  could only find BEL on when echo was enabled, but this is not
  true for debian linux.
- When using os.fpathconf on stdout under py.test in OSX, we get
  OSError, stdin does not produce any such error, so use 0 instead
  of 1.