Patch #2477: Added from __future__ import unicode_literals

The new PyParser_*Ex() functions are based on Neal's suggestion and initial patch. The new __future__ feature makes all '' and r'' unicode strings. b'' and br'' stay (byte) strings.
diff --git a/Lib/__future__.py b/Lib/__future__.py
index ea14bf3..9156459 100644
--- a/Lib/__future__.py
+++ b/Lib/__future__.py
@@ -54,6 +54,7 @@
     "absolute_import",
     "with_statement",
     "print_function",
+    "unicode_literals",
 ]
 
 __all__ = ["all_feature_names"] + all_feature_names
@@ -68,6 +69,7 @@
 CO_FUTURE_ABSOLUTE_IMPORT = 0x4000 # perform absolute imports by default
 CO_FUTURE_WITH_STATEMENT  = 0x8000   # with statement
 CO_FUTURE_PRINT_FUNCTION  = 0x10000   # print function
+CO_FUTURE_UNICODE_LITERALS = 0x20000 # unicode string literals
 
 class _Feature:
     def __init__(self, optionalRelease, mandatoryRelease, compiler_flag):
@@ -120,3 +122,7 @@
 print_function = _Feature((2, 6, 0, "alpha", 2),
                           (3, 0, 0, "alpha", 0),
                           CO_FUTURE_PRINT_FUNCTION)
+
+unicode_literals = _Feature((2, 6, 0, "alpha", 2),
+                            (3, 0, 0, "alpha", 0),
+                            CO_FUTURE_UNICODE_LITERALS)