linux-user/syscall: Add support for clock_gettime64/clock_settime64

linux-user/syscall: Add support for clock_gettime64/clock_settime64

Add support for the clock_gettime64/clock_settime64 syscalls.

If your host is 64-bit or is 32-bit with the *_time64 syscall then the
timespec will correctly be a 64-bit time_t. Otherwise the host will
return a 32-bit time_t which will be rounded to 64-bits. This will be
incorrect after y2038.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <4a7fd05532400d10aa0f684c9043e2ac7b34d91c.1584051142.git.alistair.francis@wdc.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>