aclocal: create local directory where to install m4 files

aclocal: create local directory where to install m4 files

Fixes automake bug#8168 and bug#10816.

A call like "aclocal -I m4 --install" used to fail if the 'm4'
directory wasn't pre-existing.  This could be particularly
annoying when running in a checked-out version from a VCS like
git, which doesn't allow empty directories to be tracked.

* aclocal.in (File::Path): New import.
(scan_m4_dirs): Don't die if the first directory of type FT_USER
doesn't exist and the '--install' option was given; that directory
will be created later ...
(install_file): ... here.  Change signature of this function: now
it takes as second argument the destination directory rather than
the destination file.  Crate the destination directory if it
doesn't already exist.  In verbose mode, tell what is being copied
where.
(write_aclocal): Update to the changes in 'install_file'.
* NEWS, THANKS: Update.
* tests/aclocal-install-fail.test: New test.
* tests/aclocal-install-mkdir.test: Likewise.
* tests/aclocal-no-install-no-mkdir.test: Likewise.
* tests/aclocal-verbose-install.test: Likewise.
* tests/list-of-tests.mk: Add them.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>