plugin aesgcm: use 12 bytes Initialisation Vector: SàT was using 16 bytes IV when sending files withr AES-GCM, due to ChatSecure being only compatible with that. Monal, an other iOS client is only compatible with 12 bytes IV, and ChatSecure has fixed its code to also handle 12 bytes IV, so there is not reason anymore to use 16 bytes, and SàT now uses 12 bytes.

# XXX: the Monkey Patch is here and not in src/__init__ to avoir issues with pyjamas compilation
# TODO: remove this when changes are merged in Wokkel
from sat_tmp.wokkel import install
install()