yacc: "make clean" removes .c and .h files from non-distributed .y Previously, while automake did *not* distribute C source and header files derived from non-distributed Yacc sources, it still caused them to be removed only by "make maintainer-clean" only, and not by simply "make clean" or "make distclean". This caused "make distcheck" to fail, unless the developer put those generated .c and .h files in CLEANFILES or in DISTCLEANFILES by hand. This change fixes this issue, by making non-distributed `.c' and `.h' files generated by non-distributed Yacc sources cleaned by "make clean". * tests/automake.in (lang_yacc_target_hook): Make C source and header files derived from non-distributed Yacc files cleaned by "make clean", not only by "make maintainer-clean". * tests/yacc-clean.test: New test. * tests/Makefile.am (TESTS): Update. * NEWS: Update.