cue/token: rename names for & and |

This is shorter, nicer and nicely indicates the analogy
with && and ||, as well as logic.

It also reads nicer:

a: >=3 & <=5 // a is GEQ 3 AND LEQ 5.

b: 1 | 2     // b is 1 OR 2

Change-Id: Idb1077aaedfff05478028572a718ee3e9e8a0463
Reviewed-on: https://cue-review.googlesource.com/c/1561
Reviewed-by: Marcel van Lohuizen <mpvl@google.com>
diff --git a/cue/ast.go b/cue/ast.go
index 3ca7fd5..9bfc98e 100644
--- a/cue/ast.go
+++ b/cue/ast.go
@@ -477,7 +477,7 @@
 
 	case *ast.BinaryExpr:
 		switch n.Op {
-		case token.DISJUNCTION:
+		case token.OR:
 			d := &disjunction{baseValue: newExpr(n)}
 			v.addDisjunctionElem(d, n.X, false)
 			v.addDisjunctionElem(d, n.Y, false)
@@ -506,7 +506,7 @@
 func (v *astVisitor) addDisjunctionElem(d *disjunction, n ast.Node, mark bool) {
 	switch x := n.(type) {
 	case *ast.BinaryExpr:
-		if x.Op == token.DISJUNCTION {
+		if x.Op == token.OR {
 			v.addDisjunctionElem(d, x.X, mark)
 			v.addDisjunctionElem(d, x.Y, mark)
 			return