More configurable crypto and ssl library initialization

1.  In addition to overriding the default application name,
    one can now also override the configuration file name
    and flags passed to CONF_modules_load_file().

2.  By default we still keep going when configuration file
    processing fails.  But, applications that want to be strict
    about initialization errors can now make explicit flag
    choices via non-null OPENSSL_INIT_SETTINGS that omit the
    CONF_MFLAGS_IGNORE_RETURN_CODES flag (which had so far been
    both undocumented and unused).

3.  In OPENSSL_init_ssl() do not request OPENSSL_INIT_LOAD_CONFIG
    if the options already include OPENSSL_INIT_NO_LOAD_CONFIG.

4.  Don't set up atexit() handlers when called with INIT_BASE_ONLY.

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7986)