Rename 'Standard Gaming Platform' to 'sgp' (#246)

* rename 'Standard Gaming Platform' to 'sgp'

* Adapt CMakeLists.txt files to renamed SGP directory

* Lowercase it

sgp/timer.h

@@ -0,0 +1,30 @@
+#ifndef __TIMER_
+#define __TIMER_
+
+#include "types.h"
+
+typedef UINT32 TIMER;
+
+#define MAIN_TIMER_ID	1
+
+#define MILLISECONDS(a) (a)
+#define SECONDS(a)			((a) / 1000)
+#define MINUTES(a)			(SECOND((a)) / 60)
+#define HOURS(a)				(MINUTES((a)) / 60)
+#define DAYS(a)					(HOURS((a)) / 24)
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+BOOLEAN InitializeClockManager(void);
+void	ShutdownClockManager(void);
+TIMER	GetClock(void);
+TIMER	SetCountdownClock(UINT32 TimeToElapse);
+UINT32	ClockIsTicking(TIMER uiTimer);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif