Apply typo fixes from Julio M. Merino Vidal

[SVN r27513]

doc/tutorial/details.html

@@ -105,8 +105,8 @@ invoke a lambda expression, you should always pass it to
 to in lieu of using <tt class="literal"><span class="pre">lambda</span></tt> and invoking the result &quot;manually.&quot;</dd>
 <dt>Lazy evaluation.</dt>
 <dd>A strategy of delaying evaluation until a result is
-required, thereby avoiding any unneccessary computation and any
-associated unneccessary errors.  Metafunctions are only invoked
+required, thereby avoiding any unnecessary computation and any
+associated unnecessary errors.  Metafunctions are only invoked
 when we access their nested <tt class="literal"><span class="pre">::type</span></tt>s, so we can supply all
 of their arguments without performing any computation and
 delay evaluation to the last possible moment.</dd>