ac_buildpath, ac_top_buildpath, ac_srcpath, and ac_top_srcpath.
(_AC_OUTPUT_FILES): Also substitute srcpath, top_srcpath,
builddir, buildpath, top_builddir, and top_buildpath.
(_AC_OUTPUT_SUBDIRS): Compute the dir variables *before* changing
the current directory.
* lib/autoconf/general.m4 (_AC_INIT_HELP): Compute the dir
variables *before* changing the current directory.
Skip nonexistent dirs.
* doc/autoconf.texi (Preset Output Variables): Document these
variables.
* lib/autotest/general.m4: Do not reset AT_victims.
Don't compute at_srcdir nor at_top_srcdir.
* tests/tools.at: Hence use top_srcdir.
* tests/Makefile.am, tests/autoconf, tests/autoheader,
* tests/autom4te, tests/autoreconf, tests/autoupdate, tests/ifnames:
Remove.
* tests/autoreconf.in, tests/wrappl.in, tests/autom4te.in,
* tests/wrapsh.in, tests/autoupdate.in: New.
* tests/Makefile.am (DISTCLEANFILES, EXTRA_DIST): Adjust.
* configure.ac: Build the position independent wrappers.
* man/Makefile.am: Now that test wrappers are position
independent, use them and drop dark envvar magic.
