AC_PROG_LIBTOOL was replaced by
LT_INIT in libtool 2 in 2008,
so it's time to rely on it.
Clears autoconf warnings:
configure.ac:38: warning: The macro `AC_LIBTOOL_WIN32_DLL' is obsolete. configure.ac:38: You should run autoupdate. aclocal.m4:11889: AC_LIBTOOL_WIN32_DLL is expanded from... configure.ac:38: the top level configure.ac:38: warning: AC_LIBTOOL_WIN32_DLL: Remove this warning and the call to _LT_SET_OPTION when you configure.ac:38: put the 'win32-dll' option into LT_INIT's first parameter. ./lib/autoconf/general.m4:2434: AC_DIAGNOSE is expanded from... aclocal.m4:11889: AC_LIBTOOL_WIN32_DLL is expanded from... configure.ac:38: the top level configure.ac:39: warning: The macro `AC_PROG_LIBTOOL' is obsolete. configure.ac:39: You should run autoupdate. aclocal.m4:3465: AC_PROG_LIBTOOL is expanded from... configure.ac:39: the top level libtoolize: Consider adding 'AC_CONFIG_MACRO_DIRS([m4])' to configure.ac, libtoolize: and rerunning libtoolize and aclocal.