Preparation for v0.5.1 release.
Bumping version for development.
autoconf: look for htonll in arpa/inet.h

htonll maybe defined as a macro, look for it in the arpa/inet.h. CMake build
system already does the right thing.

Fixes #206
Add usable YCM configuration file.
ssl: Fix a bug that host name verification failure isn't reported

There is an unexpected local variable shadowing in
amqp_ssl_socket_open(). So the following code is meaningless
unexpectedly.

    status = AMQP_STATUS_SSL_HOSTNAME_VERIFY_FAILED
Suppress OpenSSL deprecation warnings on OSX
Enable compiler warnings with Clang
Add platform, version, copyright client properties

Add 'platform' 'version', 'copyright' client-properties to start-ok method
during connection handshake.

Adapted from:
https://github.com/synety-jdebp/rabbitmq-c/commit/e3c76e1887ff50378f6146167daa024dbd7d4eeb
by: Jonathan de Boyne Pollard <jonathan.de.boyne.pollard@synety.com>