add sections on tgetpass changes

UPGRADE

@@ -25,6 +25,9 @@ o Upgrading from a version prior to 1.7.0:
     in sudo's ldap.conf unless ldap.conf references a valid certificate
     authority file(s).
 
+    Please also see the WHATSNEW file for a list of new features in
+    sudo 1.7.0.
+
 o Upgrading from a version prior to 1.6.9:
 
     Starting with sudo 1.6.9, if an OS supports a modular authentication

WHATSNEW

@@ -65,3 +65,12 @@ What's new in Sudo 1.7.0?
  * A new flag, -n, may be used to indicate that sudo should not
    prompt the user for a password and, instead, exit with an error
    if authentication is required.
+
+ * If sudo needs to prompt for a password and it is unable to disable
+   echo (and no askpass program is defined), it will refuse to run
+   unless the "visiblepw" Defaults option has been specified.
+
+ * Prior to version 1.7.0, hitting enter/return at the Password: prompt
+   would exit sudo.  In sudo 1.7.0 and beyond, this is treated as
+   an empty password.  To exit sudo, the user must press ^C or ^D
+   at the prompt.