[wwwdocs] Link from gcc-4.{6,7}/changes.html to porting_to.html

[Tobias Burnus]

I intent to commit the attached patch to link

from http://gcc.gnu.org/gcc-4.6/changes.html to 
http://gcc.gnu.org/gcc-4.6/porting_to.html
and
from http://gcc.gnu.org/gcc-4.7/changes.html to 
http://gcc.gnu.org/gcc-4.7/porting_to.html

Seemingly no one has written a porting-to document for 4.5 - and a 
similar link already exists for 4.4: from 
http://gcc.gnu.org/gcc-4.4/changes.html

Tobias
Index: gcc-4.6/changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.6/changes.html,v
retrieving revision 1.137
diff -p -u -r1.137 changes.html
--- gcc-4.6/changes.html	12 Jan 2012 19:35:28 -0000	1.137
+++ gcc-4.6/changes.html	12 Jan 2012 20:49:31 -0000
@@ -13,6 +13,9 @@
 
 <h2>Caveats</h2>
   <ul>
+    <li>More information on porting to GCC 4.6 from previous versions of
+    GCC can be found in the <a href="porting_to.html">porting guide</a>
+    for this release.</li>
 
     <li>The options <code>-b &lt;<em>machine</em>&gt;</code> and
     <code>-V &lt;<em>version</em>&gt;</code> have been removed because
Index: gcc-4.7/changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.7/changes.html,v
retrieving revision 1.73
diff -p -u -r1.73 changes.html
--- gcc-4.7/changes.html	12 Jan 2012 19:35:29 -0000	1.73
+++ gcc-4.7/changes.html	12 Jan 2012 20:49:32 -0000
@@ -15,6 +15,10 @@
 <h2>Caveats</h2>
 
   <ul>
+    <li>More information on porting to GCC 4.7 from previous versions of
+    GCC can be found in the <a href="porting_to.html">porting guide</a>
+    for this release.</li>
+
     <li><p>Support for a number of older systems and recently
     unmaintained or untested target ports of GCC has been declared
     obsolete in GCC 4.7.  Unless there is activity to revive them, the