move libc related stuff out of platform.h

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

util-linux/volume_id/get_devname.c

@@ -7,11 +7,12 @@
  *
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
-
+#include <sys/mount.h> /* BLKGETSIZE64 */
+#if !defined(BLKGETSIZE64)
+# define BLKGETSIZE64 _IOR(0x12,114,size_t)
+#endif
 #include "volume_id_internal.h"
 
-//#define BLKGETSIZE64 _IOR(0x12,114,size_t)
-
 static struct uuidCache_s {
 	struct uuidCache_s *next;
 //	int major, minor;