* wrappers for malloc, realloc and free that check the return values and call a
  error handler on failure
* function now() that returns second since 1st Jan 1970
* use now() from utils.c
* use xmalloc, xrealloc() and xfree() from utils.c
* add utils.c to sources
* use xmalloc, xrealloc and xfree from utils.c
* expand usage