Added global variable lm_enabled_logfiles_bitmask which holds a bit for each enbaled logfile. It is updated when situation changes.
gateway.c
Changed gateway.c:main so that command-line argument -f specifies either the name of config file in $MAXSCALE_HOME/etc or exact location and name of it. Updated README correspondingly.
Added eternal variable lm_enabled_logfiles_bitmask to be used for quick check before calling logging library functions.