doc: fix broken links in 1.7 release docs

Change-Id: Ibf73ee7be4591393f4e08d464edfa325c3ec2c11
Reviewed-on: https://go-review.googlesource.com/32798Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.7.html

@@ -43,7 +43,7 @@ includes the <a href="#context">context package</a>, promoted from the
 and now used in the standard library;
 and <a href="#testing">adds support in the testing package</a> for
 creating hierarchies of tests and benchmarks.
-The release also <a href="#cmd/go">finalizes the vendoring support</a>
+The release also <a href="#cmd_go">finalizes the vendoring support</a>
 started in Go 1.5, making it a standard feature.
 </p>
 
@@ -394,9 +394,9 @@ This allows the use of contexts for cancelation, timeouts, and passing
 request-scoped data in other standard library packages,
 including
 <a href="#net">net</a>,
-<a href="#net/http">net/http</a>,
+<a href="#net_http">net/http</a>,
 and
-<a href="#os/exec">os/exec</a>,
+<a href="#os_exec">os/exec</a>,
 as noted below.
 </p>