Merge pull request slevithan#148 from GerHobbelt/patch-comment-typo

comment typo fix

Author: slevithan

src/xregexp.js

@@ -60,7 +60,7 @@ var hasFlagsProp = /x/.flags !== undefined;
 var toString = {}.toString;
 
 function hasNativeFlag(flag) {
-    // Can't check based on the presense of properties/getters since browsers might support such
+    // Can't check based on the presence of properties/getters since browsers might support such
     // properties even when they don't support the corresponding flag in regex construction (tested
     // in Chrome 48, where `'unicode' in /x/` is true but trying to construct a regex with flag `u`
     // throws an error)