Add olm_session_describe

See merge request matrix-org/olm!9

instead of having a static one, as that could end up taking up a
lot of memory if your app keeps olm sessions hanging about.

As a way to dump the state of an olm session, ie. the chain indicies,
so we can debug why olm sessions break and get out of sync.

Build the js objects without PIC

See merge request matrix-org/olm!8

Fix comment and also js build

See merge request matrix-org/olm!7

This confuses emscripten now

The python that searches the header files for exports isn't smart
enough to know what is a comment and what isn't, so it picks this
up too and emscripten then complains about it being undefined.

Update megolm.md

See merge request matrix-org/olm!6

Without this, it's not possible to run the install or install-debug
rules multiple times.

Signed-off-by: Trygve Aaberge <trygveaa@gmail.com>

tests: Drop hypothesis from the python tests.

See merge request matrix-org/olm!5

Python unicode decode errors when decrypting.

See merge request matrix-org/olm!4

This is needed because the function returns Unicode strings and the
comparison will fail under python2 unless Unicode literals are used.

Hypothesis isn't used anymore and the strings are now constants, meaning
that the hashes should never match.

Hypothesis recently had some problems with the typing module breaking
the tox tests.

Since Hypothesis isn't really used much in the test this patch removes
it from them as well as from the test-requirements.

explicitly define backward & forward secrecy

See merge request matrix-org/olm!3

The to_native_str function was supposed to produce Unicode decoded
native strings for python2 and python3.

Upon further consideration this doesn't make much sense since under
python2 it would need to decode the bytes into a Unicode string and turn
it back into a python2 str.

The ability to use the replacement character requires us to use a
Unicode string under python2 as well.

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.

as it repeatedly trips people up, including me

Convert docs from RST to Markdown

See merge request matrix-org/olm!2

as per https://github.com/matrix-org/olm/issues/15.
thanks to @dest