log: Add pr_quelled helper

If we need to check if current loglevel will suppress
our messagess (say you need to run pr_debug in a cycle)
we can use this helper to eliminate unneded calls.

Like
  if (!pr_quelled(LOG_DEBUG)) {
    ... do something specific to LOG_DEBUG ...
  }
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/log.h

@@ -27,4 +27,9 @@ extern int write_pidfile(int pid);
 extern void print_data(unsigned long addr, unsigned char *data, size_t size);
 extern void print_image_data(int fd, unsigned int length, int show);
 
+static inline int pr_quelled(unsigned int loglevel)
+{
+	return log_get_loglevel() < loglevel && loglevel != LOG_MSG;
+}
+
 #endif /* __CR_LOG_H__ */