[AC (pkgs)] Suppressions for macro error finder

This patch adds the ability to remove certain names from the list of miscompiled macros generated by gen-macro-err.awk. Each line in the file macro.suppress (in the top-level directory of the package tree) should contain the name of one macro to NOT complain about. Stephen Turnbull requested this feature so that we can strip out all the read-event and set-buffer-multibyte complaints in the current report.