log: new object logging support

So that we can provide the specific object id in every log associated
to a given object.

src/tests/test-modem-helpers.c

@@ -4502,7 +4502,8 @@ test_bcd_to_string (void *f, gpointer d)
 /*****************************************************************************/
 
 void
-_mm_log (const char *loc,
+_mm_log (gpointer obj,
+         const char *loc,
          const char *func,
          guint32 level,
          const char *fmt,