Remove support for single-line special comments (except for //jshint)

Single-line special comments make more harm than good. Closes jshintGH-881.

src/stable/lex.js

@@ -445,6 +445,12 @@ Lexer.prototype = {
 					return;
 				}
 
+				// Don't recognize any special comments other than jshint for single-line
+				// comments. This introduced many problems with legit comments.
+				if (label === "//" && str !== "jshint") {
+					return;
+				}
+
 				if (body.substr(0, str.length) === str) {
 					isSpecial = true;
 					label = label + str;

tests/stable/unit/core.js

@@ -27,7 +27,7 @@ exports.testCustomGlobals = function (test) {
 
 	// Regression test (GH-665)
 	code = [
-		"//global bar",
+		"/*global bar*/",
 		"foo = {};",
 		"bar = {};"
 	];