Fix bug that connection window is consumed excessively

Previously we consider bytes as consumed in spdylay_session_mem_recv()
even if it is not ignored and is passing to application.  As a result,
excessive number of bytes are considered as consumed and library sends
excessive amount of WINDOW_UPDATE to peer.  This commit fixes this
bug.
Update NEWS
Bump up version number to 1.3.1 and LT revision to 8:1:1
Bump up version number to 1.3.2-DEV