Fix compile errors on Linux

direct/src/plugin/p3dConditionVar.cxx

@@ -18,6 +18,7 @@
 #include <sys/time.h>
 #include <math.h>
 #endif
+#include <errno.h>
 
 ////////////////////////////////////////////////////////////////////
 //     Function: P3DConditionVar::Constructor

direct/src/plugin/p3dInstance.h

@@ -137,7 +137,7 @@ private:
   string _shared_filename;
   SubprocessWindowBuffer *_swbuffer;
   char *_reversed_buffer;
-#endif __APPLE__
+#endif  // __APPLE__
 
   P3DSplashWindow *_splash_window;
   bool _instance_window_opened;