Fix the build with gcc 4.4 and newer versions of libtool.

Fix the build with gcc 4.4 and newer versions of libtool.

configure.in: Update AC_PREREQ to autoconf 2.64.  Use LT_INIT instead
  of AC_PROG_LIBTOOL.  Remove the deprecated AC_TYPE_SIGNAL (which we
  didn't use anyway).  Fix the indentation of the explanatory text for
  --without-kevent and --with-win32.

src/sar.c: Convert "struct sockaddr_storage" to "void *" to comply
  with C99's strict(er) aliasing rules.  Allocate off the stack or
  heap, as appropriate.  Add new function sar_free_nameserver() to
  clean up the heap-allocated data.