doc: fix small HTML problems

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/14629043

doc/code.html

@@ -296,7 +296,7 @@ package newmath
 // Sqrt returns an approximation to the square root of x.
 func Sqrt(x float64) float64 {
 	z := 1.0
-	for i := 0; i < 1000; i++ {
+	for i := 0; i &lt; 1000; i++ {
 		z -= (z*z - x) / (2 * z)
 	}
 	return z

doc/codewalk/codewalk.xml

@@ -42,7 +42,7 @@
 	its <code>src</code> is just a file name.
 </step>
 
-<step title="Specifiying a source line" src='doc/codewalk/codewalk.xml:/title="Title"/'>
+<step title="Specifying a source line" src='doc/codewalk/codewalk.xml:/title="Title"/'>
 	The most complex part of the codewalk specification is
 	saying what lines to highlight.
 	Instead of ordinary line numbers,