nestlog: streamlining + comments + markdown

include/nestlog/log_level.hpp

@@ -5,13 +5,28 @@
 namespace xo {
     enum class log_level : std::uint32_t {
         /* control log message severity
-         *   silent > severe > error > warning > info > chatty
+         *   silent > always > severe > error > warning > info > chatty > never
+         *
+         * never:
+         *   used internally e.g. by XO_ENTER1()
+         *   a log message with this severity will never be printed
+         *
+         * always:
+         *   use with XO_ENTER1():
+         *     scope log(XO_ENTER1(always, mydebug_flag));
+         *   to log message whenever mydebug_flag is true (for any .min_log_level except silent)
+         *
+         * silent:
+         *   use in log_config to suppress all log messages
          */
+        never,
+        verbose,
         chatty,
         info,
         warning,
         error,
         severe,
+        always,
         silent,
 
         default_level = error