Exit upon `install' failure, part one.

Exit upon `install' failure, part one.

* lib/am/data.am (install-%DIR%%PRIMARY%): Exit if any install
command fails.
* lib/am/python.am (install-%DIR%PYTHON): Likewise.
* lib/am/scripts.am (install-%DIR%SCRIPTS): Likewise.
* lib/am/texinfos.am (install-dvi-am, install-html-am)
(install-info-am:, install-pdf-am): Likewise.
* tests/instmany.test: New test, for SCRIPTS, DATA, and HEADERS.
* tests/instmany-python.test: New test, for PYTHON.
* tests/Makefile.am: Adjust.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>