Modernize, improve and/or extend test scripts `conf*.test'. * tests/confh5.test: Cosmetic changes. * tests/conff.test: Likewise. * tests/confdeps.test: Likewise. * tests/conflnk.test: Likewise. * tests/conflnk2.test: Likewise. * tests/confsub.test: Likewise. * tests/confvar.test: Likewise, and make grepping of Makefile.in stricter. * tests/confvar2.test: Likewise. * tests/conflnk3.test: Cosmetic changes, and re-enable a temporarly disabled test (which didn't work with autoconf <= 2.59, but now we are requiring autoconf 2.62, so...) * tests/conflnk4.test: Cosmetic changes, and extend existing tests accordingly to "TODO" comments. * tests/conff2.test: Make grepping of Automake's stderr stricter. Add some comments explaining why we don't use the `configure.in' stub preset be ./defs. * tests/confh.test: Use the `configure.in' stub created by ./defs, rather than writing one from scratch, and do not call AC_OUTPUT. Enable `errexit' shell flag, and related changes. Prefer diff over cmp to compare text files. Prefer perl over sed to fetch the value of $(DIST_COMMON) from Makefile.in. Make grepping of the contents of $(DIST_COMMON) stricter. * tests/confh4.test: Use the `configure.in' stub created by ./defs, rather than writing one from scratch. Make grepping of Makefile.in stricter. * tests/confh5.test: Make grepping of `config.h' stricter. Add a comment. * tests/configure.test: Avoid obsolescent constructs in generated `configure.ac'. Do not write `configure.in' two times. Escape literal dots in grep regular expressions. * tests/confincl.test: Enable `errexit' shell flag, and related changes. Prefer fgrep over grep. Other cosmetic changes. * tests/config.test: Renamed to ... * tests/confh6.test: ... this. Fix m4 quoting in `configure.in', and make grepping of `config.h' and `config.h.in' stricter. * tests/conf2.test: Renamed ... * tests/confh7.test: ... to this. Use the `configure.in' stub created by ./defs, rather than writing one from scratch. Try to run the checks both with and without AC_PROG_CC and AC_OUTPUT in `configure.in'. * tests/Makefile.am (TESTS): Updated.