Add spdylay_session_consume() API

This function is back ported from nghttp2 project.  This is a
preferred way to manually control flow window.
SPDYLAY_OPT_NO_AUTO_WINDOW_UPDATE is not deprecated.  New application
should use SPDYLAY_OPT_NO_AUTO_WINDOW_UPDATE2 and use
spdylay_session_consume() to tell the library how many bytes
application consumed.
Bump up version number to 1.3.0-DEV