fix(serverHandler): use strings.Replace instead of strings.ReplaceAll

Prevent using `strings.ReplaceAll` to make it possible to compile under
Go 1.10. Thus, make it possible to build executable run under Windows
XP.

Author: marjune163

src/serverHandler/upload.go

@@ -58,7 +58,7 @@ func (h *handler) saveUploadFiles(fsPrefix string, createDir, overwriteExists bo
 			break
 		}
 
-		partFilename := path.Clean(strings.ReplaceAll(part.FileName(), "\\", "/"))
+		partFilename := path.Clean(strings.Replace(part.FileName(), "\\", "/", -1))
 		if partFilename[0] == '/' {
 			partFilename = partFilename[1:]
 		}