This patch changes the decryption functions not to fail if there was an
unicode decode error while converting the decrypted bytes plaintext into
a native python string.
Characters that cannot be decoded as unicode are now replaced with the
unicode replacement character (U+FFFD).
The old behaviour of raising an UnicodeDecodeError can be achieved by
passing the "strict" error handling scheme to the decrypt function.
This patch adds bindings to the PK part of the Olm library contained in
the pk.h header file.
Encryption, decryption as well as pickling/unpickling of the decryption
object is supported.
Signed-off-by: Damir Jelić <poljar@termina.org.uk>
