Work in progress to support a speed factor in SITL

These contains some rough changes trying to get SITL to speed up by a
SPEED_FACTOR.

This platform time code probably requires some more thought and refactor
but this gets a demo at 4x working.

src/include/visibility.h

@@ -73,6 +73,12 @@
 #define system_sleep sleep
 #pragma GCC poison sleep
 
+#include <pthread.h>
+#define system_pthread_cond_timedwait pthread_cond_timedwait
+// We can't poison pthread_cond_timedwait because it seems to be used in the
+// <string> include.
+
+
 #ifdef __cplusplus
 #include <cstdlib>
 #endif

src/platforms/px4_time.h

@@ -2,6 +2,7 @@
 
 #include <sys/types.h>
 #include <time.h>
+#include <pthread.h>
 
 #if defined(__PX4_APPLE_LEGACY)
 
@@ -31,10 +32,29 @@ __END_DECLS
 
 #else
 
+
+#if 0
 #define px4_clock_gettime clock_gettime
 #define px4_clock_settime clock_settime
 
 #define px4_usleep system_usleep
 #define px4_sleep system_sleep
+#define px4_pthread_cond_timedwait system_pthread_cond_timedwait
+#else
+
+
+__BEGIN_DECLS
+__EXPORT int px4_clock_gettime(clockid_t clk_id, struct timespec *tp);
+__EXPORT int px4_clock_settime(clockid_t clk_id, const struct timespec *tp);
+
+__EXPORT int px4_usleep(useconds_t usec);
+__EXPORT unsigned int px4_sleep(unsigned int seconds);
+__EXPORT int px4_pthread_cond_timedwait(pthread_cond_t *cond,
+					pthread_mutex_t *mutex,
+					const struct timespec *abstime);
+__END_DECLS
+#endif
+
+
 
 #endif