Changes for CryptX

TODO:
        - consider: RSA->check_key, RSA password protected keys
        - consider: PK->encrypt|decrypt ... add $armour param and make it compatible with Crypt::RSA
        - maybe add xxx_b64url alternatives (e.g. sha1_b64url ...)
        - croak with the "real caller" (Crypt::Mac::*, Crypt::Mode::*, ...)
        - croak when mode does not call start_(en|de)crypt
        - make random_string faster (implement in XS)
        - "libtom-src/bn_mp_invmod.c", line 37: warning: statement not reached
        - solaris failure: http://ppm4.activestate.com/sun4-solaris/5.14/1400/M/MI/MIK/CryptX-0.011.d/log-20130615T021640.txt
        - solaris failure: http://ppm4.activestate.com/sun4-solaris/5.12/1200/M/MI/MIK/CryptX-0.012.d/log-20130617T182847.txt (after rsa.t ok 29 - verify, dsa.t ok 27 - decrypt)
          DSA: my $sig = $pr1->sign("message");
          RSA: my $k = Crypt::PK::RSA->new; $k->generate_key(256, 65537);

0.013   2013/08/28
        - DSA/RSA/ECC/DH - importing keys from string changed - now: $pk->import_key(\$buffer_with_key)
        - DSA/RSA/ECC/DH - size() and is_private() now return undef if no key loaded
        - improved RSA doc

0.012   2013/06/17
        - README, LICENSE etc. to improve CPANTS score
        - somehow works with perl 5.6.2

0.011   2013/06/15
        - fixing various compiler warnings

0.009   2013/05/19
        - doc fixes
        - requires perl 5.8.8 or higher
        - INCOMPATIBILITY: all digest related 'xxx_base64' functions renamed to 'xxx_b64'

0.008   2013/05/02
        - fixed prng test failures
        - Crypt::Digest::* croaks with the "real caller" (not a nice solution)

0.007   2013/04/23
        - Crypt::PRNG supports add_entropy() - without params
        - Crypt::PRNG fork-safe & thread-safe
        - random_string has default $len = 20
        - doc fixes
        - cpan tester failure fix for pk_dsa.t

0.006   2013/04/19
        - added Crypt::KeyDerivation
        - Win64 compatibility

0.005   2013/04/18
        - added Crypt::PRNG::Fortuna|RC4|Sober128|Yarrow
        - added Crypt::PK::RSA|DSA|ECC|DH

0.004   2013/04/16
        - removing illegal Crypt::Random

0.003   2013/04/16
        - added Crypt::Mode::CBC|CFB|CTR|ECB|OFB
        - added Crypt::AuthEnc::CCM|EAX|GCM|OCB

0.002   2013/04/11
        - first release on CPAN