Fix config.status depfiles failure. * m4/depout.m4 (_AM_OUTPUT_DEPENDENCY_COMMANDS): Commands are again a single shell brace group, so they are correctly skipped when dependencies are turned off. The failure is noisy with ksh only. * tests/depend6.test: New test. * tests/Makefile.am: Adjust. * THANKS: Update. Report and different suggested patch by Markus Duft. Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>