Fix potentially-exponential regular expression in use-strict-scanning

Author: marijnh

acorn/src/parseutil.js

@@ -6,7 +6,7 @@ const pp = Parser.prototype
 
 // ## Parser utilities
 
-const literal = /^(?:'((?:\\.|[^'])*?)'|"((?:\\.|[^"])*?)")/
+const literal = /^(?:'((?:\\.|[^'\\])*?)'|"((?:\\.|[^"\\])*?)")/
 pp.strictDirective = function(start) {
   for (;;) {
     // Try to find string literal.