Provide framework for auto initialise/deinitialise of the library

This commit provides the basis and core code for an auto initialisation
and deinitialisation framework for libcrypto and libssl. The intention is
to remove the need (in many circumstances) to call explicit initialise and
deinitialise functions. Explicit initialisation will still be an option,
and if non-default initialisation is needed then it will be required.
Similarly for de-initialisation (although this will be a lot easier since
it will bring all de-initialisation into a single function).

Reviewed-by: Richard Levitte <levitte@openssl.org>