configure.ac: Make autoreconf run cleanly on cent5

First, it turns out that autoconf 2.59 actually works out. Second,
AC_PROG_LIBTOOL should be used by autoconf projects when they use
libtool - at least older versions. Third, the m4 directory isn't checked
in and isn't autocreated, so remove the AC_CONFIG_MACRO_DIR again - if
you want to use it, go do something sane with m4. I'm not a fan of m4.

Signed-off-by: Robin Sonefors <robin.sonefors@op5.com>