fix some typos in the documentation

Fixes #196.

R=rsc
https://golang.org/cl/154152

doc/effective_go.html

@@ -977,14 +977,14 @@ you can pass a pointer to the array.
 
 <pre>
 func Sum(a *[3]float) (sum float) {
-	for _, v := range a {
+	for _, v := range *a {
 		sum += v
 	}
 	return
 }
 
 array := [...]float{7.0, 8.5, 9.1};
-x := sum(&amp;array);  // Note the explicit address-of operator
+x := Sum(&amp;array);  // Note the explicit address-of operator
 </pre>
 
 <p>

doc/go_tutorial.html

@@ -550,7 +550,7 @@ declaration on line 31; it declares <code>r</code> and <code>e</code> to hold th
 both of type <code>int</code> (although you'd have to look at the <code>syscall</code> package
 to see that).  Finally, line 35 returns two values: a pointer to the new <code>File</code>
 and the error.  If <code>syscall.Open</code> fails, the file descriptor <code>r</code> will
-be negative and <code>NewFile</code> will return <code>nil</code>.
+be negative and <code>newFile</code> will return <code>nil</code>.
 <p>
 About those errors:  The <code>os</code> library includes a general notion of an error.
 It's a good idea to use its facility in your own interfaces, as we do here, for
@@ -1279,7 +1279,7 @@ code that invokes the operation and responds to the request:
 19    }
 </pre>
 <p>
-Line 18 defines the name <code>binOp</code> to be a function taking two integers and
+Line 14 defines the name <code>binOp</code> to be a function taking two integers and
 returning a third.
 <p>
 The <code>server</code> routine loops forever, receiving requests and, to avoid blocking due to

doc/go_tutorial.txt

@@ -841,7 +841,7 @@ code that invokes the operation and responds to the request:
 
 --PROG progs/server.go /type.binOp/ /^}/
 
-Line 18 defines the name "binOp" to be a function taking two integers and
+Line 14 defines the name "binOp" to be a function taking two integers and
 returning a third.
 
 The "server" routine loops forever, receiving requests and, to avoid blocking due to