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.

Also don't compare ALPN identifier with streq, since they are just
byte string.

Cipher suites are chosen by DHE and ECDHE ciphers + GCM (AEAD).  Now
default cipher list is the one recommended by Mozilla web site.  The
--honor-cipher-order option is removed and now it is always assumed.

Conflicts:
	lib/nghttp2_session.c

Now local and remote settings values are stored in dedicated structure
nghttp2_settings_storage.

ALTSVC and BLOCKED frames are now extension frames.  To add new
extension frame without modifying nghttp2_frame union, which causes so
name bump, we separated extension frames from core frames.
nghttp2_frame includes generic nghttp2_extension.  The payload member
of nghttp2_extension will point to the structure of extension frame
payload.  The frame types of extension frames are defined in
nghttp2_ext_frame_type.

Now SSL/TLS option mask to disable particular SSL/TLS protocol
versions are pre-calculated and stored in Config.

CONTINUATION now doesn't have padding.

Unexpected CONTINUATION frame is handled separately as connection
error.

I have this error with some old gcc (4.6) release (Ubuntu 12.04 or Travis...)

Mainly make nested code block to rather flat style.