eina_log optimization: allow to compile out some debug messages.

eina_log optimization: allow to compile out some debug messages.

Users may opt to set EINA_LOG_LEVEL_MAXIMUM to some integer and macro
will then evaluate to check for that value before actually call
eina_log_print() macro. By using optimizations compilers will
effectivelly compile out the code if it is never reached, thus saving
the check and function call in possible critical paths.

git-svn-id: http://svn.enlightenment.org/svn/e/trunk/eina@42269 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33