Unbreak on FreeBSD

../clients/window.c:42:10: fatal error: 'sys/epoll.h' file not found
 #include <sys/epoll.h>
          ^~~~~~~~~~~~~
../shared/xalloc.c:39:28: error: use of undeclared identifier 'program_invocation_short_name'
                fprintf(stderr, "[%s] ", program_invocation_short_name);
                                         ^