Log Message:
chat/lurch-purple: Update to 0.6.8

Changes:

* Makefile adaptations should help building and running this for some. Thanks \ 
for the pull requests.
* Fixed some bugs regarding carbons and sending messages to yourself, also added \ 
NULL checks so that it plays nicer with other plugins which might set the \ 
message to NULL
* Update submodules and their dependencies, most importantly \ 
libsignal-protocol-c to 2.3.2
* Add plugin preferences prototype: Single option is logging verbosity on the \ 
debug log