Support older style (Windows) CSR headers and footers

[eidorb]

Use grep regular expressions to match older style headers

-----BEGIN NEW CERTIFICATE REQUEST-----
...
-----END NEW CERTIFICATE REQUEST-----

in addition to the standard

-----BEGIN CERTIFICATE REQUEST-----
...
-----END CERTIFICATE REQUEST-----

The older style headers are present in CSRs created by Windows certreq.

There is a discussion on the headers here: https://stackoverflow.com/questions/28628744/is-there-a-spec-for-csr-begin-headers