* configure.ac: Export @am_AUTOCONF@. * tests/defs.in (AUTOCONF): Define as @am_AUTOCONF@, not @AUTOCONF@, so the test suite runs `autoconf' and not `missing --run autoconf'. * tests/missing.test, tests/missing2.test: Arrange for missing to be used in front of autoconf even if the user has exported AUTOCONF. This fixes two spurious failures reported by Mark D. Baushke.