Warning fixes

I've gone through and cleaned up all the Astron related warnings. Apple depreciated OpenSSL for Crypto when OS X 10.7 was released (If memory serves me right, or something along those lines) so all those warnings are still present, however Astron still runs fine. These are all just minor fixes, but they have been bugging me for quite some time.

I have tested this and everything appears to run A-OK :+1: 
By example...

	private:
		int m_exit_code;

	public:
		ShutdownException(int exit_code);
		int exit_code() const;
		virtual const char* what();

Instead of...

    using exception::what;
	private:
		int m_exit_code;

	public:
		ShutdownException(int exit_code);
		int exit_code() const;
		const char* what();