all/windows: Be case in-sensitive about pattern matching. (#3682)

Resource strings and paths are case insensitive on windows
deployments but if user happens to use upper case instead of
lower case for certain configuration params like bucket
policies and bucket notification config. We might not honor
them which leads to a wrong behavior on windows.

This is windows only behavior, for all other platforms case
is still kept sensitive.

cmd/posix-list-dir-others.go

@@ -52,10 +52,6 @@ func readDir(dirPath string) (entries []string, err error) {
 			return nil, err
 		}
 		for _, fi := range fis {
-			// Skip special files, if found.
-			if hasPosixReservedPrefix(fi.Name()) {
-				continue
-			}
 			// Stat symbolic link and follow to get the final value.
 			if fi.Mode()&os.ModeSymlink == os.ModeSymlink {
 				var st os.FileInfo