Add source/fix-fcntl.h to define missing O_EXLOCK, O_SHLOCK and O_CLOEXEC as 0, and remove implementation unit System.File_Control
Make new directory nls, and add platform-depended text encoding as System.Native_Encoding
Add overloaded System.Native_Encoding.Convert and improve System.Native_Encoding.Generic_String
Reorder
Remark
Change substitutes of System.Native_Encoding