On platforms that are not officially supported by GNU Autotools (like OS/2)
it is necessary to generate configure and other related stuff using platform-specific
Autoconf and Automake to make the build succeed. A script autoconf.sh added
by this commit does that.
Note that it's necessary to remove pre-generated upstream versions of these files
from Git completely in order to avoid seeing multiple differences resulting from
different versions of Autotools (and also to save some space - configure files
are huge).
This commit also adds a few minor bits to configure.ac/Makefile.am of a few
projects to help autoconf.sh do its job properly.
Needed for #2.
