[haxe mode] Add 'abstract' keyword

Author: as3boyan

mode/haxe/haxe.js

@@ -16,7 +16,7 @@ CodeMirror.defineMode("haxe", function(config, parserConfig) {
       "function": kw("function"), "catch": kw("catch"), "untyped": kw("untyped"), "callback": kw("cb"),
       "for": kw("for"), "switch": kw("switch"), "case": kw("case"), "default": kw("default"),
       "in": operator, "never": kw("property_access"), "trace":kw("trace"),
-    "class": type, "enum":type, "interface":type, "typedef":type, "extends":type, "implements":type, "dynamic":type,
+    "class": type, "abstract":type, "enum":type, "interface":type, "typedef":type, "extends":type, "implements":type, "dynamic":type,
       "true": atom, "false": atom, "null": atom
     };
   }();