[CRIU] soccr breaks build on older kernels

[Adrian Reber]

On my RHEL7 based system the kernel (or the include files) doesn't know about
TCP_TIMESTAMP and builds are broken now on those systems:

make[1]: Entering directory `/share/criu'
  CC       soccr/soccr.o
soccr/soccr.c: In function ‘get_stream_options’:
soccr/soccr.c:157:37: error: ‘TCP_TIMESTAMP’ undeclared (first use in this function)
   ret = getsockopt(sk->fd, SOL_TCP, TCP_TIMESTAMP, &val, &auxl);
                                     ^
soccr/soccr.c:157:37: note: each undeclared identifier is reported only once for each function it appears in
soccr/soccr.c: In function ‘libsoccr_set_sk_data_noq’:
soccr/soccr.c:406:35: error: ‘TCP_TIMESTAMP’ undeclared (first use in this function)
   if (setsockopt(sk->fd, SOL_TCP, TCP_TIMESTAMP,
                                   ^
make[1]: *** [soccr/soccr.o] Error 1
make[1]: Leaving directory `/share/criu'
make: *** [soccr/built-in.o] Error 2

		Adrian