Bugfix 1119552: PKCS#1 v1.5 accepts signature without the optional NULL parameters

Hi,

This is a fix for bug 1119552:

https://bugs.launchpad.net/pycrypto/+bug/1119552

It now allows the PKCS#1 v1.5 signature verification routine to accept signatures where the digest information does not contain the optional NULL parameters.

I branched it out my pkc8 branch purely to allow the statement:

    if mhash.oid.startswith("1.2.840.113549.2."):

where Object ID is a string, as opposed to a hard-to-interpret binary string.