nacl: update instructions for new SDK

R=nigeltao_gnome, nigeltao
CC=golang-dev
https://golang.org/cl/2253042

src/pkg/exp/nacl/README

-Native Client support is still incomplete:
-Native Client does not yet allow runtime code generation,
-so Go's many uses of closures do not work.
-
 To try Native Client by running 4s (tetris) or 5s or Spacewar:
 
 1. Build the Go distribution for your native system.
 
-2. Download Native Client and install it.
-	http://nativeclient.googlecode.com/svn/trunk/src/native_client/documentation/getting_started.html
-    * You can stop after step 4 on those instructions
-    (the ./scons --prebuilt firefox_install).
+2. Download the Native Client SDK and install it.
+    http://code.google.com/p/nativeclient-sdk/wiki/HowTo_GetStarted
+  * You only need to do steps 1 and 2.
 
-3. (optional) Install "./build/native_client/scons-out/opt-*/staging/sel_ldr"
+3. Copy "./native_client*/toolchain/*/bin/sel_ldr"
    from the Native Client distribution somewhere in your path as "nacl".
-   This will let you run binaries using "nacl 8.out".
+   This will let you run binaries using "nacl -M 8.out".
+   The -M flag enables multithreaded access to the video library.
 
 4. Build the Go distribution again, this time for Native Client:
 	cd $GOROOT/src
@@ -22,15 +18,19 @@ To try Native Client by running 4s (tetris) or 5s or Spacewar:
    * If you are on a Mac, your dock will flicker as the "nacl" binary
    starts and stops while the tests run.  You can stop the tests at any time.
 
-5. Run "godoc --http=:5103".
-   * This will run the godoc built for your host OS, not Native Client,
-   because all-nacl.bash doesn't install a nacl godoc.
-   * Note that there is a colon before the 5103 in the argument
-   (shorthand for 0.0.0.0:5103).
-   * The port must be 5103: that's the only port that Native Client
-   trusts to run binaries from.
-
-6. Open Firefox and visit one of:
+5. Run the programs by using
+	nacl -M $GOROOT/src/pkg/exp/4s/8.out
+	nacl -M $GOROOT/src/pkg/exp/4s/8.5s
+	nacl -M $GOROOT/src/pkg/exp/spacewar/8.out
+	
+6. If you have an old copy of the Native Client plugin, you may be
+   able to run the programs in your browser, by running
+   "godoc --http=:5103" and then visiting
   * http://localhost:5103/src/pkg/exp/4s/4s.html
   * http://localhost:5103/src/pkg/exp/4s/5s.html [sic]
   * http://localhost:5103/src/pkg/exp/spacewar/spacewar.html
+
+   This usage is deprecated in favor of newere APIs in recent
+   releases of Native Client.  More work will be necessary to support
+   interactive graphics when using those releases.
+