THRIFT-929. cpp: Add tests to verify blocking read behavior

THRIFT-929. cpp: Add tests to verify blocking read behavior

Add tests that check to see whether or not read() and borrow() block
when called with a length larger than the amount of data currently
available.

At the moment, not all of the transports behave the same way.  I believe
the desired behavior is:

  When M bytes are available, and 0 < M < N:
  - read(N): return M bytes immediately
  - borrow(N): return NULL immediately

  When 0 bytes are available:
  - read(N): In this case, it is acceptable either to immediately return
    0, or to block until some data is available.  If the transport
    blocks, it returns immediately when some date becomes available,
    even if less than N bytes are available.
  - borrow(N): return NULL immediately

- The borrow() tests fail when using TBufferedTransport.
  TBufferedTransport incorrectly blocks until the amount of data
  requested is available.

- test_read_none_available() fails when using TFramedTransport.
  Calling read() on a TFramedTransport when no data is available throws
  an exception instead of returning 0.

- test_read_none_available() fails when using TFDTransport.  This is
  partly just an artifact of the fact that I use SIGALRM as part of this
  test.  Unlike TSocket, TFDTransport doesn't retry after EINTR.

- test_read_part_available() fails when using TZlibTransport around a
  transport that has blocking read() behavior.  TZlibTransport::read()
  loops calling read() on the underlying transport.  It should probably
  break out of the loop and return to the caller as soon as it has
  uncompressed any data, even if it is less than requested and more
  might be available.  Once some data has been uncompressed,
  TZlibTransport cannot risk calling read() again since it might block.

Will commit fixes for these separately.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@1005160 13f79535-47bb-0310-9956-ffa450edef68