sync actual changes from newer mongodb

Index: src/mongo/db/fts/unicode/gen_casefold_map.py
--- src/mongo/db/fts/unicode/gen_casefold_map.py.orig
+++ src/mongo/db/fts/unicode/gen_casefold_map.py
@@ -13,7 +13,7 @@ def generate(unicode_casefold_file, target):
     The case folding function contains a switch statement with cases for every
     Unicode codepoint that has a case folding mapping.
     """
-    out = open(target, "w")
+    out = open(target, "w", encoding='utf-8')
 
     out.write(getCopyrightNotice())
     out.write(include("mongo/db/fts/unicode/codepoints.h"))
@@ -22,7 +22,7 @@ def generate(unicode_casefold_file, target):
 
     case_mappings = {}
 
-    cf_file = open(unicode_casefold_file, 'rU')
+    cf_file = open(unicode_casefold_file, 'r', encoding='utf-8')
 
     for line in cf_file:
         # Filter out blank lines and lines that start with #
