Require a space after the enum keyword (#143)

This stops us confusing enum declarations with enum values that happen
to start `enum_foo`.

Author: Wilfred

syntaxes/hack.json

@@ -698,7 +698,7 @@
           ]
         },
         {
-          "begin": "(?i)^\\s*(enum)\\s*(class)\\s+([a-z0-9_]+)\\s*:?",
+          "begin": "(?i)^\\s*(enum)\\s+(class)\\s+([a-z0-9_]+)\\s*:?",
           "beginCaptures": {
             "1": {
               "name": "storage.modifier.php"
@@ -723,7 +723,7 @@
           ]
         },
         {
-          "begin": "(?i)^\\s*(enum)\\s*([a-z0-9_]+)\\s*:?",
+          "begin": "(?i)^\\s*(enum)\\s+([a-z0-9_]+)\\s*:?",
           "beginCaptures": {
             "1": {
               "name": "storage.type.enum.php"

syntaxes/test/enums.hack

@@ -2,6 +2,8 @@ enum SimpleEnum: int as arraykey {
   X = 1;
   Y = 2;
   Z = 3;
+  ENUM_FOO = 1;
+  ENUM_CLASS_BAR = 2;
 }
 
 enum ComplicatedEnum: classname<Foo> as classname<Bar> {}