Stats: use monotonic clock instead of GTimer

Reduce GLib usage.

src/Main.cxx

@@ -554,7 +554,6 @@ int mpd_main(int argc, char *argv[])
 	archive_plugin_deinit_all();
 #endif
 	config_global_finish();
-	stats_global_finish();
 	io_thread_deinit();
 	SignalHandlersFinish();
 	delete instance;

src/Stats.cxx

@@ -30,9 +30,11 @@
 #include "Log.hxx"
 
 #ifndef WIN32
-#include <glib.h>
-
-static GTimer *uptime;
+/**
+ * The monotonic time stamp when MPD was started.  It is used to
+ * calculate the uptime.
+ */
+static unsigned start_time;
 #endif
 
 static DatabaseStats stats;
@@ -40,14 +42,7 @@ static DatabaseStats stats;
 void stats_global_init(void)
 {
 #ifndef WIN32
-	uptime = g_timer_new();
-#endif
-}
-
-void stats_global_finish(void)
-{
-#ifndef WIN32
-	g_timer_destroy(uptime);
+	start_time = MonotonicClockS();
 #endif
 }
 
@@ -107,7 +102,7 @@ stats_print(Client &client)
 #ifdef WIN32
 		      GetProcessUptimeS(),
 #else
-		      (unsigned)g_timer_elapsed(uptime, NULL),
+		      MonotonicClockS() - start_time,
 #endif
 		      (unsigned long)(client.player_control.GetTotalPlayTime() + 0.5));
 

src/Stats.hxx

@@ -24,8 +24,6 @@ class Client;
 
 void stats_global_init(void);
 
-void stats_global_finish(void);
-
 void stats_update(void);
 
 void

src/system/Clock.cxx

@@ -30,6 +30,28 @@
 #endif
 #endif
 
+unsigned
+MonotonicClockS(void)
+{
+#ifdef WIN32
+	return GetTickCount() / 1000;
+#elif defined(__APPLE__) /* OS X does not define CLOCK_MONOTONIC */
+	static mach_timebase_info_data_t base;
+	if (base.denom == 0)
+		(void)mach_timebase_info(&base);
+
+	return (unsigned)((mach_absolute_time() * base.numer / 1000)
+			  / (1000000 * base.denom));
+#elif defined(CLOCK_MONOTONIC)
+	struct timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return ts.tv_sec;
+#else
+	/* we have no monotonic clock, fall back to time() */
+	return time(nullptr);
+#endif
+}
+
 unsigned
 MonotonicClockMS(void)
 {

src/system/Clock.hxx

@@ -24,6 +24,13 @@
 
 #include <stdint.h>
 
+/**
+ * Returns the value of a monotonic clock in seconds.
+ */
+gcc_pure
+unsigned
+MonotonicClockS();
+
 /**
  * Returns the value of a monotonic clock in milliseconds.
  */