libsystemd: translate leading log <LEVEL> in stderr logging

This commit also switches the stdout/stderr log capture backend for all
notify:systemd services from the sysklogd project's logger tool to the
bundled logit tool.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

libsystemd/sd-daemon.h

@@ -6,6 +6,16 @@
 
 #define SD_LISTEN_FDS_START 3
 
+/* systemd logging defines for stderr parsing by Finit */
+#define SD_EMERG    "<0>"  /* system is unusable */
+#define SD_ALERT    "<1>"  /* action must be taken immediately */
+#define SD_CRIT     "<2>"  /* critical conditions */
+#define SD_ERR      "<3>"  /* error conditions */
+#define SD_WARNING  "<4>"  /* warning conditions */
+#define SD_NOTICE   "<5>"  /* normal but significant condition */
+#define SD_INFO     "<6>"  /* informational */
+#define SD_DEBUG    "<7>"  /* debug-level messages */
+
 /* Basic notification function */
 int sd_notify(int unset_environment, const char *state);