Add code and changes to implement the ENGINE mechanism. These are the

Add code and changes to implement the ENGINE mechanism.  These are the
patches that Geoff had in a patch file in his play directory.

NOTE for openssl-cvs:  THIS IS A CVS BRANCH (BRANCH_engine).  IT IS
NOT FOR THE FAINTHEARTED TO PLAY WITH.  The code works as it is, but
it's not at all sure it ends up in the OpenSSL distributio in this
form, so do not get dependent on it!

Those rsyncing the repository are considered warned!