Check directory names for unportable names. Shaking the code to check this also led to the removal of the no-"/"-in-SUBDIRS restriction, and a fix to _do_recursive_traversal. * automake.in (check_directory): New function extracted from handle_subdirs, and augmented to check for reserved W32/DOS name. (check_directories_in_var): New function. (handle_subdirs): Call check_directories_in_var. Doing so also suppress the restriction that SUBDIRS should not contain slashes. (scan_autoconf_traces) <AC_CONFIG_AUX_DIR>: Call check_directory to ensure the argument exists and is safe. * doc/automake.texi (Top level): Do not say that src/subdir cannot be put in SUBDIRS. (Dist): Mention that distdir and top_distdir can be absolute. * lib/Automake/Variable.pm (_do_recursive_traversal) Support undefined $fun_collect, and fix two bugs introduced with skip_ac_subst on 2004-03-07. * lib/am/distdir.am (distdir): Use absolute distdir and top_distdir when recursing, because we can no longer prepend only `..' in case of SUBDIRS with `/'. * tests/auxdir4.test, tests/subdir9.test: New files. * tests/Makefile.am (TESTS): Add auxdir4.test. * tests/cond2.test, tests/subdir7.test: Augment to check location in diagnostics.