multiple: fix a few typos

- Duplicate words
- change -> chance
- insure -> ensure (this is actually an Americanism, but can confuse
  some people)

en_US.ISO8859-1/htdocs/ipv6/w6d.xml

@@ -136,7 +136,7 @@
 
     <h3>Why is IPv6 not enabled by default?</h3>
     <p>IPv6 has a mandatory link-local address.
-      In times where many people are are also using FreeBSD on their mobile
+      In times where many people are also using FreeBSD on their mobile
       computers and joining random networks the services they started would
       be accessible by other people on the same network.  This may also happen
       if they only started the services for IPv4 and are not aware of IPv6 at

en_US.ISO8859-1/htdocs/multimedia/multimedia-input.xml

@@ -2688,7 +2688,7 @@
 	<item source="bsdtalk" added="20070519">
 	    <title>Qing Li and Tatuya Jinmei</title>
 	    <desc>
-		Interview at at BSDCan with Qing Li and Tatuya
+		Interview at BSDCan with Qing Li and Tatuya
 		Jinmei. We talk about the books that they authored
 		with Keiichi Shima: "IPv6 Core Protocols Implementation"
 		and "IPv6 Advanced Protocols Implementation." The
@@ -12376,7 +12376,7 @@
 		of the project was a set of documents which identifies
 		possible threats for the TCP and IP protocols and,
 		where possible, proposes counter-measures to mitigate
-		the identified threats. This presentation will will
+		the identified threats. This presentation will
 		describe some of the new insights that were gained
 		as a result of this project. Additionally, it will
 		provide an overview of the state of affairs of the
@@ -13072,7 +13072,7 @@
 		on the system. One of the first problems presented
 		to the person who wants to tune the scheduler is
 		how to measure the effects of their changes. Simply
-		tweaking the parameters and hoping that that will
+		tweaking the parameters and hoping that will
 		help is not going to lead to good results. In our
 		recent experiments we have used the top(1) program
 		to measure our results.

en_US.ISO8859-1/htdocs/portmgr/charter.xml

@@ -43,7 +43,7 @@
   </li>
 
   <li>
-    <p>Work with the FreeBSD Security team to insure that security
+    <p>Work with the FreeBSD Security team to ensure that security
       problems are indentified and handled in a timely fashion.</p>
   </li>
 

en_US.ISO8859-1/htdocs/portmgr/qa.xml

@@ -161,8 +161,8 @@ two main categories:
     <p>Remove expired ports.  Ports that have been marked BROKEN for
       some time are marked DEPRECATED (with an EXPIRATION_DATE) and then
       are removed if no one has fixed them by that time.  The intent of
-      this this process is to try to insure that if a user installs a port,
-      there is the best possible change that it can be made to work.</p>
+      this process is to try to ensure that if a user installs a port,
+      there is the best possible chance that it can be made to work.</p>
 
     <p>In other cases, ports are marked DEPRECATED when they have been
       replaced by a newer version and the older version is no longer