added BangPatterns to fix the installation errors

Data/Text/Encoding/Utf16.hs

-{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE MagicHash, BangPatterns #-}
 
 -- |
 -- Module      : Data.Text.Encoding.Utf16

Data/Text/Encoding/Utf8.hs

-{-# LANGUAGE CPP, MagicHash #-}
+{-# LANGUAGE CPP, MagicHash, BangPatterns #-}
 
 -- |
 -- Module      : Data.Text.Encoding.Utf8