Add a hook for sudoers parse errors (including defaults and aliases).

The hook can be used to log parser errors (sudoers module) or keep
track of which files have an error (visudo).
Previously, we only kept track of a single parse error.

plugins/sudoers/audit.c

@@ -181,7 +181,7 @@ sudoers_audit_open(unsigned int version, sudo_conv_t conversation,
     info.settings = settings;
     info.user_info = user_info;
     info.plugin_args = plugin_options;
-    ret = sudoers_init(&info, submit_envp);
+    ret = sudoers_init(&info, log_parse_error, submit_envp);
 
     if (ret == true) {
 	/* Unset close function if we don't need it to avoid extra process. */