add python bindings for PK signing

OLMKit: add Short Authentication String verification

(cherry picked from commit add1bd6e4250012dcfa30a40d763dba82f53c254)

(cherry picked from commit ff31d489c68d5d9e597bd55a6f6a64f3fe4c7ecc)

(cherry picked from commit 934d516eb35c488ee197e1bab78a4c81e3c8241d)

(cherry picked from commit 3e954ca2729d3333ea853c878602d1696f616573)

(cherry picked from commit c0a53ebaeda420f636698b99c393868d2bf8f905)

Java binding for SAS

Fix / missing free() on some errors


Added doc regarding string encoding for keys


cleaning

The SAS header is required to build the package therefore it needs to be
shipped with the source distribution of the package.

Adding it to the manifest achieves this.

because older versions of emscripten don't support the length argument to
UTF8ToString.

The Pointer_stringify() function is deprecated and has a couple of
issues because it tries to guess the encoding of the buffer. In some
cases it can ignore the length parameter which could end up in
inconsistencies.

Switch to UTF8toString() that takes a length parameter and respects,
that way we don't need to allocate an additional byte for a NULL byte.

This allows downstream users to install this python module with pip as
well as allowing people to declare it as a dependency in their setup.py.

Signed-off-by: Damir Jelić <poljar@termina.org.uk>

This patch adds the Olm header files to the manifest, this results in
the header files being added to source distributions of the python-olm
module.

The headers are required to build the module. Including them in the
source distribution is the easiest way to make sure that builds from the
source distribution will succeed provided that the Olm C library is
already installed.

Signed-off-by: Damir Jelić <poljar@termina.org.uk>

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>

Typing is part of standard library from python 3.5 and from python 3.7
onwards trying to install it results in an error.

This patch disables typing installation on python versions that are
newer than 3.5.

Signed-off-by: Damir Jelić <poljar@termina.org.uk>

Signed-off-by: Damir Jelić <poljar@termina.org.uk>

This patch adds bindings to the SAS part of the Olm library contained in
the sas.h header file.

Signed-off-by: Damir Jelić <poljar@termina.org.uk>

Add signing class to the pk module

because emscripted has dropped support for the old flag and us
setting it is now breaking the build.

This is a workaround for a bug where signature verification would
overwrite the variable holding the signature.

This only happens on python2.

Signed-off-by: Damir Jelić <poljar@termina.org.uk>