spec: examples of untyped boolean, string constants

This is a spec correction, not a language change.
The implementations have behaved like this for years
(and there are tests to that effect), and elsewhere in
the spec true and false are defined to be untyped
boolean constants.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5477047

doc/go_spec.html

@@ -3408,7 +3408,7 @@ untyped complex constant yields an untyped complex constant.
 
 <p>
 A constant <a href="#Comparison_operators">comparison</a> always yields
-a constant of type <code>bool</code>. If the left operand of a constant
+an untyped boolean constant. If the left operand of a constant
 <a href="#Operators">shift expression</a> is an untyped constant, the
 result is an integer constant; otherwise it is a constant of the same
 type as the left operand, which must be of integer type
@@ -3427,8 +3427,11 @@ const d = 1 &lt;&lt; 3.0         // d == 8     (untyped integer constant)
 const e = 1.0 &lt;&lt; 3         // e == 8     (untyped integer constant)
 const f = int32(1) &lt;&lt; 33   // f == 0     (type int32)
 const g = float64(2) &gt;&gt; 1  // illegal    (float64(2) is a typed floating-point constant)
-const h = "foo" &gt; "bar"    // h == true  (type bool)
-const j = 'w' + 1          // j == 'x'   (untyped character constant)
+const h = "foo" &gt; "bar"    // h == true  (untyped boolean constant)
+const j = true             // j == true  (untyped boolean constant)
+const k = 'w' + 1          // k == 'x'   (untyped character constant)
+const l = "hi"             // l == "hi"  (untyped string constant)
+const m = string(k)        // m == "x"   (type string)
 const Σ = 1 - 0.707        //            (untyped complex constant)
 const Δ = Σ + 2.0e-4       //            (untyped complex constant)
 const Φ = iota*1i - 1/1i   //            (untyped complex constant)