New implementation for os.sameFile on Windows

Hard-links on Windows are now treated just as they are on POSIX.
The new implementation is faster than the previous, but still it's quite
slower than fstat (use with caution).

lib/windows/winlean.nim

@@ -47,6 +47,22 @@ type
     dwProcessId*: int32
     dwThreadId*: int32
 
+  TFILETIME* {.final, pure.} = object ## CANNOT BE int64 BECAUSE OF ALIGNMENT
+    dwLowDateTime*: DWORD
+    dwHighDateTime*: DWORD
+  
+  TBY_HANDLE_FILE_INFORMATION* {.final, pure.} = object
+    dwFileAttributes*: DWORD
+    ftCreationTime*: TFILETIME
+    ftLastAccessTime*: TFILETIME
+    ftLastWriteTime*: TFILETIME
+    dwVolumeSerialNumber*: DWORD
+    nFileSizeHigh*: DWORD
+    nFileSizeLow*: DWORD
+    nNumberOfLinks*: DWORD
+    nFileIndexHigh*: DWORD
+    nFileIndexLow*: DWORD
+
 const
   STARTF_USESHOWWINDOW* = 1'i32
   STARTF_USESTDHANDLES* = 256'i32
@@ -149,14 +165,11 @@ const
 
   MAX_PATH* = 260
 type
-  FILETIME* {.final, pure.} = object ## CANNOT BE int64 BECAUSE OF ALIGNMENT
-    dwLowDateTime*: int32
-    dwHighDateTime*: int32
   TWIN32_FIND_DATA* {.pure.} = object
     dwFileAttributes*: int32
-    ftCreationTime*: FILETIME
-    ftLastAccessTime*: FILETIME
-    ftLastWriteTime*: FILETIME
+    ftCreationTime*: TFILETIME
+    ftLastAccessTime*: TFILETIME
+    ftLastWriteTime*: TFILETIME
     nFileSizeHigh*: int32
     nFileSizeLow*: int32
     dwReserved0: int32
@@ -192,13 +205,13 @@ proc FreeEnvironmentStringsA*(para1: cstring): int32 {.
 
 proc GetCommandLineA*(): CString {.importc, stdcall, dynlib: "kernel32".}
 
-proc rdFileTime*(f: FILETIME): int64 = 
+proc rdFileTime*(f: TFILETIME): int64 = 
   result = ze64(f.dwLowDateTime) or (ze64(f.dwHighDateTime) shl 32)
 
 proc rdFileSize*(f: TWin32FindData): int64 = 
   result = ze64(f.nFileSizeLow) or (ze64(f.nFileSizeHigh) shl 32)
 
-proc GetSystemTimeAsFileTime*(lpSystemTimeAsFileTime: var FileTime) {.
+proc GetSystemTimeAsFileTime*(lpSystemTimeAsFileTime: var TFILETIME) {.
   importc: "GetSystemTimeAsFileTime", dynlib: "kernel32", stdcall.}
 
 proc Sleep*(dwMilliseconds: int32){.stdcall, dynlib: "kernel32",
@@ -209,12 +222,16 @@ proc ShellExecute*(HWND: THandle, lpOperation, lpFile,
                    nShowCmd: int32): THandle{.
     stdcall, dynlib: "shell32.dll", importc: "ShellExecuteA".}
 
+proc GetFileInformationByHandle*(hFile: THandle,
+  lpFileInformation: ptr TBY_HANDLE_FILE_INFORMATION): WINBOOL{.
+    stdcall, dynlib: "kernel32", importc: "GetFileInformationByHandle".}
+
 const
   WSADESCRIPTION_LEN* = 256
   WSASYS_STATUS_LEN* = 128
   FD_SETSIZE* = 64
   MSG_PEEK* = 2
-  
+ 
   INADDR_ANY* = 0
   INADDR_LOOPBACK* = 0x7F000001
   INADDR_BROADCAST* = -1
@@ -410,6 +427,9 @@ const
   GENERIC_READ* = 0x80000000'i32
   GENERIC_ALL* = 0x10000000'i32
   FILE_SHARE_READ* = 1'i32
+  FILE_SHARE_DELETE* = 4'i32
+  FILE_SHARE_WRITE* = 2'i32
+ 
   CREATE_ALWAYS* = 2'i32
   OPEN_EXISTING* = 3'i32
   FILE_BEGIN* = 0'i32
@@ -421,6 +441,8 @@ const
   FILE_MAP_WRITE* = 2'i32
   INVALID_FILE_SIZE* = -1'i32
 
+  FILE_FLAG_BACKUP_SEMANTICS* = 33554432'i32
+
 proc CreateFileA*(lpFileName: cstring, dwDesiredAccess, dwShareMode: DWORD,
                   lpSecurityAttributes: pointer,
                   dwCreationDisposition, dwFlagsAndAttributes: DWORD,