core, log: make libraries logging use the MM level and format

The log level of the libraries was not honoring the log level
configured in MM, so we would see debug messages reported even if the
default log level configured was INFO or MSG.

The format of the logs emitted by the libraries was also not following
the format of the rest of MM logs, e.g. they would not include timing
info in the logs which would make it hard to follow certain event
transitions.

Make the libraries logging use the ModemManager logging method, to fix
all those issues.

src/mm-log.c

@@ -96,8 +96,8 @@ mm_to_syslog_priority (MMLogLevel level)
     return 0;
 }
 
-static int
-glib_to_syslog_priority (GLogLevelFlags level)
+static MMLogLevel
+glib_level_to_mm_level (GLogLevelFlags level)
 {
     /* if the log was flagged as fatal (e.g. G_DEBUG=fatal-warnings), ignore
      * the fatal flag for logging purposes */
@@ -106,17 +106,15 @@ glib_to_syslog_priority (GLogLevelFlags level)
 
     switch (level) {
     case G_LOG_LEVEL_ERROR:
-        return LOG_CRIT;
     case G_LOG_LEVEL_CRITICAL:
-        return LOG_ERR;
+        return MM_LOG_LEVEL_ERR;
     case G_LOG_LEVEL_WARNING:
-        return LOG_WARNING;
+        return MM_LOG_LEVEL_WARN;
     case G_LOG_LEVEL_MESSAGE:
-        return LOG_NOTICE;
     case G_LOG_LEVEL_INFO:
-        return LOG_INFO;
+        return MM_LOG_LEVEL_INFO;
     case G_LOG_LEVEL_DEBUG:
-        return LOG_DEBUG;
+        return MM_LOG_LEVEL_DEBUG;
     case G_LOG_LEVEL_MASK:
     case G_LOG_FLAG_FATAL:
     case G_LOG_FLAG_RECURSION:
@@ -249,7 +247,8 @@ _mm_log (gpointer     obj,
     }
 
 #if defined MM_LOG_FUNC_LOC
-    g_string_append_printf (msgbuf, "[%s] %s(): ", loc, func);
+    if (loc && func)
+        g_string_append_printf (msgbuf, "[%s] %s(): ", loc, func);
 #endif
 
     if (obj)
@@ -268,11 +267,17 @@ _mm_log (gpointer     obj,
 
 static void
 log_handler (const gchar    *log_domain,
-             GLogLevelFlags  level,
+             GLogLevelFlags  glib_level,
              const gchar    *message,
              gpointer        ignored)
 {
-    log_backend (NULL, NULL, glib_to_syslog_priority (level), message, strlen (message));
+    _mm_log (NULL, /* obj */
+             NULL, /* module */
+             NULL, /* loc */
+             NULL, /* func */
+             glib_level_to_mm_level (glib_level),
+             "%s",
+             message);
 }
 
 gboolean