* tests/ansi10.test: Use AC_PROG_CC_STDC. Fix test that ac_cv_prog_cc_stdc isn't just used by Automake code in `configure'. * tests/ansi6.test, tests/ansi7.test: Likewise. * tests/ansi9.test: Likewise. Do not override by setting $U and $(ANSI2KNR) at `make' time; that will be fragile. * tests/libobj8.test: Use AC_PROG_CC_STDC. * tests/subobj3.test: Likewise. Use `set -e'.