doc: mention new DWARF line table decoder in go1.5.html

Change-Id: I4e8c20284255e0e17b6fb72475d2d37f49994788
Reviewed-on: https://go-review.googlesource.com/13113Reviewed-by: Rob Pike <r@golang.org>

doc/go1.5.html

@@ -953,6 +953,11 @@ See for example the definition of the new type
 <a href="/pkg/debug/dwarf/#Class"><code>Class</code></a>.
 </li>
 
+<li>
+The <a href="/pkg/debug/dwarf/"><code>debug/dwarf</code></a> package
+also now supports decoding of DWARF line tables.
+</li>
+
 <li>
 The <a href="/pkg/debug/elf/"><code>debug/elf</code></a>
 package now has support for the 64-bit Power architecture.