master branch reverted

[Gavin Smith]

I've reverted the master branch up to commit 15f90529ee13 (2024-07-27)
in an attempt to restore a stable working point.  Recent attempts at
fixing the build system  (e.g. to run after "make maintainer-clean"
was run) have only made things worse.  "make distcheck" was not working
due to an attempt to rebuild pod2texi.texi in a read-only srcdir.

I have tested this by running

./autogen.sh
./configure
make
make distcheck

I hope that any further changes should at least pass this basic check.
(Unfortunately it takes a few minutes to run due to the test suite running.)