Add support for UTF-8 characters to OS.Path
Add support for UTF-8 characters to OS.Path

OS.Path.InvalidArc was raised when a path name included UTF-8 characters.
This is a bug inherited from SML/NJ 110.74.  This bug has been fixed in
upstream SML/NJ 110.75.  We fix this by importing fixed code from SML/NJ
110.75.

This commit fixes Issue #39.

smlsharp/smlsharp,smlsharp/smlsharp,smlsharp/smlsharp,smlsharp/smlsharp,smlsharp/smlsharp,smlsharp/smlsharp,smlsharp/smlsharp