Refine licence as main LICENSE and DUAL.

DUAL

@@ -0,0 +1,35 @@
+The MIT License (MIT)
+
+Copyright (c) 2013-2021 The SRS Authors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+---------------------------------------------------------------------------
+Note:
+Individual files contain the following tag instead of the full license text.
+
+	SPDX-License-Identifier: MIT or MulanPSL-2.0
+
+This enables machine processing of license information based on the SPDX
+License Identifiers that are here available: http://spdx.org/licenses/
+
+For MIT, please read https://spdx.org/licenses/MIT.html
+
+For MulanPSL-2.0, please read https://spdx.org/licenses/MulanPSL-2.0.html
+and note that MulanPSL-2.0 is compatible with Apache-2.0, please see
+https://www.apache.org/legal/resolved.html#category-a

LICENSE

@@ -18,18 +18,3 @@ FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-
----------------------------------------------------------------------------
-Note:
-Individual files contain the following tag instead of the full license text.
-
-	SPDX-License-Identifier: MIT or MulanPSL-2.0
-
-This enables machine processing of license information based on the SPDX
-License Identifiers that are here available: http://spdx.org/licenses/
-
-For MIT, please read https://spdx.org/licenses/MIT.html
-
-For MulanPSL-2.0, please read https://spdx.org/licenses/MulanPSL-2.0.html
-and note that MulanPSL-2.0 is compatible with Apache-2.0, please see
-https://www.apache.org/legal/resolved.html#category-a