spdycat: Allow -H to override built-in header fields

This change also allow users to send specify multiple same header
fields using -H if it is not built-in header fields.
Check protocol id length so that scanner don't overrun buffer
npn: Prefer higher SPDY version
spdycat: Fix bug that -H does not allow single letter header name
shrpx: Return SSL_TLSEXT_ERR_OK from servername_callback
Fix errors found by coverity scan
Fix errors found by coverity scan
shrpx: Remove Connection: close header field from CONNECT response
Update NEWS
Update http-parer to 8d9e5db981b623fffc93657abacdc80270cbee58
Update NEWS
Update sphinx_rtd_theme to 54a48b1726ed602c9b5416ee46c639462ec315fe
Update NEWS
Bump up version number to 1.2.4, LT revision to 7:3:0
Bump up version number to 1.2.5-DEV
shrpx: Set timeout to underlying bufferevent

Setting write timeout to filter bufferevent does not work as intended.
It timeouts even when there is no data to write.
Update NEWS
Bump up version number to 1.2.5
Bump up version number to 1.2.6-DEV
shrpx: Get rid of openssl filter

Libevent Openssl filter is very inconvenient in various respect.  The
most annoying thing is it somehow emits data when SSL_shutdown is
called.  The reason we introduced this filter solution is drop
connection if TLS renegotiation is detected.  This commit implements
renegotiation detection and drop connection without filtering.