+# FIXME:
+# for each .m4 file listed in the Files: section(s)
+# parse it for AC_LIBSOURCES directives, and accumulate the set
+# of files `required' via all AC_LIBSOURCES.
+# If this set is not empty, ensure that it contains
+# the same (.c and .h only?) files as are listed in the Files: sections.
+