terminate operator regexp with word boundary

Like suggested in:
bloomtime#1 (comment)

Author: TXMuc

expression.js

@@ -35,19 +35,19 @@ function word() {
 }
 
 function notop() {
-  return this.match(/^NOT/i).toUpperCase();
+  return this.match(/^NOT\b/i).toUpperCase();
 }
 
 function negation() {
   return this.seq(notop, notFactor).slice(1);
 }
 
 function conjunction() {
-  return OPTREES[this.match(/^AND/i).toUpperCase()];
+  return OPTREES[this.match(/^AND\b/i).toUpperCase()];
 }
 
 function disjunction() {
-  return OPTREES[this.match(/^OR/i).toUpperCase()];
+  return OPTREES[this.match(/^OR\b/i).toUpperCase()];
 }
 
 var OPTREES = {