#8 Support for encrypted keys

[Mark Montague]

The CosignCrypto directive references a private key file. In filters where such is possible, add support for the private key file being encrypted with a passphrase which needs to be provided before the filter will start. In parrticular, the "assistant" that generates keys and CSRs under MacOS 10.6 generates a private key file which is encrypted using a passphrase, and such key files will not currently work with mod_cosign 3.0.x. While this can be worked around by creating a second copy of the private key that is not encrypted, it would be nicer if mod_cosign could use the same copy of the private key that Apache httpd 2.2.x uses.