fixes os.moveFile on Windows

lib/pure/os.nim

@@ -1010,8 +1010,16 @@ proc copyFile*(source, dest: string) {.rtl, extern: "nos$1",
 proc moveFile*(source, dest: string) {.rtl, extern: "nos$1",
   tags: [ReadIOEffect, WriteIOEffect].} =
   ## Moves a file from `source` to `dest`. If this fails, `OSError` is raised.
-  if c_rename(source, dest) != 0'i32:
-    raise newException(OSError, $strerror(errno))
+  when defined(Windows):
+    when useWinUnicode:
+      let s = newWideCString(source)
+      let d = newWideCString(dest)
+      if moveFileW(s, d, 0'i32) == 0'i32: raiseOSError(osLastError())
+    else:
+      if moveFileA(source, dest, 0'i32) == 0'i32: raiseOSError(osLastError())
+  else:
+    if c_rename(source, dest) != 0'i32:
+      raise newException(OSError, $strerror(errno))
 
 when not declared(ENOENT) and not defined(Windows):
   when NoFakeVars:

lib/windows/winlean.nim

@@ -284,6 +284,10 @@ when useWinUnicode:
                  bFailIfExists: cint): cint {.
     importc: "CopyFileW", stdcall, dynlib: "kernel32".}
 
+  proc moveFileW*(lpExistingFileName, lpNewFileName: WideCString,
+                 bFailIfExists: cint): cint {.
+    importc: "MoveFileW", stdcall, dynlib: "kernel32".}
+
   proc getEnvironmentStringsW*(): WideCString {.
     stdcall, dynlib: "kernel32", importc: "GetEnvironmentStringsW".}
   proc freeEnvironmentStringsW*(para1: WideCString): int32 {.
@@ -308,6 +312,10 @@ else:
                  bFailIfExists: cint): cint {.
     importc: "CopyFileA", stdcall, dynlib: "kernel32".}
 
+  proc moveFileA*(lpExistingFileName, lpNewFileName: cstring,
+                 bFailIfExists: cint): cint {.
+    importc: "MoveFileA", stdcall, dynlib: "kernel32".}
+
   proc getEnvironmentStringsA*(): cstring {.
     stdcall, dynlib: "kernel32", importc: "GetEnvironmentStringsA".}
   proc freeEnvironmentStringsA*(para1: cstring): int32 {.