- myfree in pager.c was called with an argument, so add one to the
dummy definition
- pgoff is offset_t (unsigned) and doesn't need to be compared to 0
- clang says '*(int *)0 = 0' will be optimized away instead of keeping
the segfault without a volatile hint (?! that is wrong!), but it causes
no harm to add anyway.
On CentOS 7 (RHEL 7?), "errno" isn't set when vsyscall_gettimeofday
fails. So, in such case, vsyscall_gettimeofday send SIGSEGV to the
caller to report failure of gettimeofday operation.
