Add a timeout to spdycat

Add a timeout parameter to spdycat and add a crazy parameter to spdyd to test it (or test other clients)

The spdylay_data contains full of implementation details and is not
used in public API. It should be hidden.
The spdylay_frame union now only contains the control frame.

Spdylay library itself does not depend on OpenSSL. The example programs
in examples directory do. Spdylay library should be built without
OpenSSL.

Made spdylay_session_get_pri_lowest() to get the lowest priority value
for the current session.

This change allows the application code to get the lowest priority value
without knowing the protocol version which the current session uses.

We say the header block is invalid if at least one of the following
condition is true:
There are duplicate header names; or the header names are not
encoded in US-ASCII character set and not lower cased; or the
header name is zero-length string; or the header value contains
multiple in-sequence NUL bytes.

spdylay_frame_unpack_nv() returns SPDYLAY_ERR_INVALID_HEADER_BLOCK
if the unpacking suceeded but it found the header block is invalid.
This means that caller treats it as success, but do additional
processing for invalid header block if it wants.
The functions calling spdylay_frame_unpack_nv() also return
SPDYLAY_ERR_INVALID_HEADER_BLOCK.

spdylay_net.h is compatibility layer for network related header files.
In the nature of spdylay library it should not depend on the actual
networking implementations, but we need some system headers for
optimization. Currently, arpha/inet.h and netinet/in.h are needed for
ntoh*/hton* functions.

Added AC_CANONICAL_{BUILD,HOST,TARGET}

spdylay_session_mem_recv() processes input bytes as the received data
from the remote endpoint. spdylay_session_recv() uses it internally.
The spdylay_inbound_buffer and ibuf member in spdylay_session is removed.
The buffer is allocated in the stack when spdylay_session_recv() is called.