doc: mention the ppc64(le) ports in release notes

Also make the spelling consistent in asm.html

Change-Id: Ifa751eee288fe0634cd317eb827f3e408b199620
Reviewed-on: https://go-review.googlesource.com/12501Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

doc/asm.html

@@ -741,7 +741,7 @@ Addressing modes:
 
 </ul>
 
-<h3 id="ppc64">Power64, a.k.a. ppc64</h3>
+<h3 id="ppc64">Power 64, a.k.a. ppc64</h3>
 
 <p>
 The Power 64 port is in an experimental state.

doc/go1.5.html

@@ -233,6 +233,14 @@ The new port <code>linux/arm64</code> is mostly in place, but <code>cgo</code>
 is only supported using external linking.
 </p>
 
+<p>
+Also available as experiments are <code>ppc64</code> (IBM Power 64)
+and <code>ppc64le</code> (IBM Power 64, little-endian).
+Both these ports support <code>cgo</code>,
+but for <code>ppc64</code> it requires external linking while
+for <code>ppc64le</code> it requires internal linking.
+</p>
+
 <p>
 On FreeBSD, Go 1.5 requires FreeBSD 8-STABLE+ because of its new use of the <code>SYSCALL</code> instruction.
 </p>