Add poly1305 to libcrypto utilising Andrew Moon's public domain implementation.

— jsing

http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libssl/src/crypto/poly1305/poly1305-donna.c?rev=1.1

http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libssl/src/crypto/poly1305/poly1305.c?rev=1.1

http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libssl/src/crypto/poly1305/poly1305.h?rev=1.1

http://www.openbsd.org/cgi-bin/cvsweb/src/regress/lib/libcrypto/poly1305/poly1305test.c?rev=1.1