Add a full set of pkcs#1 v2 test vectors

For v1.5 we use somewhat unofficial test vectors we found on the
rsalabs FTP server. There is a little awk script which helped us to
convert them. All the test vectors are in separate files with C
tables to keep the actual test program readable.

We detected a few flaws in our pkcs1 implementation which will be
fixed with the next commit.