* aclocal.in (write_aclocal): Take an output file and list of used macros in arguments and make up the file contents here. (trace_used_macros): New function. (add_file): Do not update $output. ($output): Delete. (MAIN): Call trace_used_macros. Then rewrite aclocal.m4 only for these traced macros. This should shorten aclocal.m4 by stripping out unused macros. * automake.texi (Invoking aclocal): Document ${AUTOM4TE}. * tests/aclibobj.test: Make sure configure.in exists by the time aclocal runs. * tests/aclocal8.test: New file. * tests/Makefile.am (TESTS): Add aclocal8.test. Suggested by Bruno Haible and Akim Demaille.