sync with sudo 1.7.3

WHATSNEW

@@ -3,7 +3,7 @@ What's new in Sudo 1.8.0?
  * Sudo has been refactored to use modular framework that can
    support third-party policy and I/O logging plugins.  The default
    plugin is "sudoers" which provides the traditional sudo
-   functionality.  See the sudo_plugins manual for details on the
+   functionality.  See the sudo_plugin manual for details on the
    plugin interface and the sample plugin for a simple example.
 
 What's new in Sudo 1.7.3?
@@ -22,6 +22,14 @@ What's new in Sudo 1.7.3?
    Mac OS X, and Linux systems with the devpts filesystem (pseudo-ttys
    only).
 
+ * Sudo's SELinux support should now function correctly when running
+   commands as a non-root user and when one of stdin, stdout or stderr
+   is not a terminal.
+
+ * Sudo now uses mbr_check_membership() on systems that support it
+   to determine group membership.  Currently, only Darwin (Mac OS X)
+   supports this.
+
  * The passwd_timeout and timestamp_timeout options may now be
    specified as floating point numbers for more granular timeout
    values.