Remove __FILE__ et al as keywords.

These were keywords prior to Swift 2, and have only been kept around as
keywords to provide a custom error message to rewrite to `#file` et
al. It's incorrect to keep them as keywords, and that error should be
implemented differently if we care about it.

Author: DougGregor

gyb_syntax_support/Token.py

@@ -244,12 +244,6 @@ def macro_name(self):
     ExprKeyword('Try', 'try'),
     ExprKeyword('Throws', 'throws'),
 
-    Keyword('__FILE__', '__FILE__'),
-    Keyword('__LINE__', '__LINE__'),
-    Keyword('__COLUMN__', '__COLUMN__'),
-    Keyword('__FUNCTION__', '__FUNCTION__'),
-    Keyword('__DSO_HANDLE__', '__DSO_HANDLE__'),
-
     # Pattern keywords
     PatternKeyword('Wildcard', '_'),