15.6 Upgrading From Version 2.13
The introduction of the previous section (see section 15.5 Upgrading From Version 1) perfectly
suits this section....
Autoconf version 2.50 is mostly backward compatible with version 2.13.
However, it introduces better ways to do some things, and doesn't
support some of the ugly things in version 2.13. So, depending on how
sophisticated your `configure.ac' files are, you might have to do
some manual work in order to upgrade to version 2.50. This chapter
points out some problems to watch for when upgrading. Also, perhaps
configure scripts could benefit from some of the new
features in version 2.50; the changes are summarized in the file
`NEWS' in the Autoconf distribution.