Changes in Version 3.8 (January 2012):
PFX_MakeFile so it now creates PFX files in the exact format that OpenSSL creates
with weak 40-bit encryption of the certificate as default behaviour.
RSA_ReadPrivateKeyFromPFX to read a private key directly from
a PFX file into an internal key string.
Note that this is different from the existing RSA_GetPrivateKeyFromPFX function which
just extracts the encrypted PKCS-8 file and saves it. We try to use the convention "Read" to mean read-into-internal-string
and "Get" to mean extract-and-save-as-a-file.
X509_GetCertFromPFX to cope with encrypted certificates.
RSA_PublicKeyFromPrivate function to convert an internal private key string
into a public one. This is useful if you only have a private key file like a PFX file.