log naxsi to a specific log file

Signed-off-by: Nicolas Zin <nicolas.zin@gmail.com>
remove debug message
change log behaviour: if no naxsi_log are specified, logs got to error log
regroup all naxsi log functions into a separate file: naxsi_log.c
add naxsi_log unit test
- rename naxsi_logfile to naxsi_log (more intuitive)
- allow to have a global naxsi_log (into the main section) and in location
ngx_http_naxsi_logfile_main_conf must not be declared static
hunt memory leak (ngx_array)
change the way log go to logfiles, i.e. not going through nginx log phase, but push directly logs into files
fix compilation issue
fix compilation issue
 potential bugfix with pointer and NGX_CONF_TAKE1 instead of NGX_CONF_1MORE naxsi_log.c
check cf->args and reroute naxsi msg to error if naxsilog is removed
Merge pull request #100 from nzin/master

redirect naxsi log to a separate log file