Boot Descriptor Block (BDB) library and utilities

Building:
---------
The host-side library and utilities requires OpenSSL.

Do 'make runtests' to ensure everything is working.

Generating a BDB:
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Edit the options in bdb_create.c.  Then 'make bdb'.

In the next release, this will take a config file rather than
requiring recompilation each time.  Also, the BDB header and data will
be signed in two separate steps, so that the private BDB key is not
required each time.

Revision History:
-----------------
v0.1.2	24-Nov-2015	Add support for RSA-3072B keys and signatures.
			Add dump_rsa utility and 'make testkeys' to create
			new keys.
			Use a RSA-3072B (exponent 3) key for the subkey so
			the exponent 3 code gets tested.

v0.1.1	17-Nov-2015	Add support for ECDSA-521 data types.  Note that
			only the data types are supported; there is not a
			C implementation for ECDSA.

v0.1.0	15-Sep-2015	Initial version.