allow compositors to define the logging behavior

Signed-off-by: Giulio Camuffo <giuliocamuffo@gmail.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/src/compositor.h b/src/compositor.h
index 4600ae3..de8a3b6 100644
--- a/src/compositor.h
+++ b/src/compositor.h
@@ -1545,10 +1545,9 @@
 /* String literal of spaces, the same width as the timestamp. */
 #define STAMP_SPACE "               "
 
+typedef int (*log_func_t)(const char *fmt, va_list ap);
 void
-weston_log_file_open(const char *filename);
-void
-weston_log_file_close(void);
+weston_log_set_handler(log_func_t log, log_func_t cont);
 int
 weston_vlog(const char *fmt, va_list ap);
 int