this fixes e's logs to include eina backtraces again. this is a
shortcoming of eina_log not being able to do multiple passes basically
(multiple outputs) per log.
Summary: Use a EINA_LOG_LEVELS environment variable for setting log level instead of a E_LOG_LEVEL macro
Test Plan:
run e with EINA_LOG_LEVELS=e:4 environment variable.
we can see log messages using EINA_LOG_DOM_DBG.
Reviewers: zmike, raster, devilhorns
Reviewed By: raster
CC: cedric
Differential Revision: https://phab.enlightenment.org/D885