y2038: include: Move struct __timeval64 definition to a separate file

The struct __timeval64's definition has been moved from ./include/time.h to
./include/struct___timeval64.h.

This change would prevent from polluting other glibc namespaces (when
headers are modified to support 64 bit time on architectures with
__WORDSIZE==32).

Now it is possible to just include definition of this particular structure
when needed.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

include/struct___timeval64.h

@@ -0,0 +1,17 @@
+#ifndef _STRUCT_TIMEVAL64_H
+#define _STRUCT_TIMEVAL64_H
+
+#if __TIMESIZE == 64
+# define __timeval64 timeval
+#else
+/* The glibc Y2038-proof struct __timeval64 structure for a time value.
+   This structure is NOT supposed to be passed to the Linux kernel.
+   Instead, it shall be converted to struct __timespec64 and time shall
+   be [sg]et via clock_[sg]ettime (which are now Y2038 safe).  */
+struct __timeval64
+{
+  __time64_t tv_sec;         /* Seconds */
+  __suseconds64_t tv_usec;       /* Microseconds */
+};
+#endif
+#endif /* _STRUCT_TIMEVAL64_H  */

include/time.h

@@ -4,6 +4,7 @@
 #ifndef _ISOMAC
 # include <bits/types/struct_timeval.h>
 # include <struct___timespec64.h>
+# include <struct___timeval64.h>
 # include <bits/types/locale_t.h>
 # include <stdbool.h>
 # include <time/mktime-internal.h>
@@ -73,20 +74,6 @@ struct __itimerspec64
 };
 #endif
 
-#if __TIMESIZE == 64
-# define __timeval64 timeval
-#else
-/* The glibc Y2038-proof struct __timeval64 structure for a time value.
-   This structure is NOT supposed to be passed to the Linux kernel.
-   Instead, it shall be converted to struct __timespec64 and time shall
-   be [sg]et via clock_[sg]ettime (which are now Y2038 safe).  */
-struct __timeval64
-{
-  __time64_t tv_sec;         /* Seconds */
-  __suseconds64_t tv_usec;       /* Microseconds */
-};
-#endif
-
 #if __TIMESIZE == 64
 # define __utimbuf64 utimbuf
 # define __itimerval64 itimerval