3rdparty: add OpenJPEG library source code (tag v2.3.1)

- https://github.com/uclouvain/openjpeg/releases/tag/v2.3.1
- src/lib/openjp2
- readme files

Author: VadimLevin

3rdparty/openjpeg/AUTHORS.md

@@ -0,0 +1,21 @@
+# Authors of OpenJPEG
+See also [THANKS](https://github.com/uclouvain/openjpeg/blob/master/THANKS.md)
+
+David Janssens designed and implemented the first version of OpenJPEG.
+
+Kaori Hagihara designed and implemented the first version of OpenJPIP.
+
+Jerome Fimes implemented the alpha version of OpenJPEG 2.0.
+
+Giuseppe Baruffa added the JPWL functionalities.
+
+Mickaël Savinaud implemented the final OpenJPEG 2.0 version based on a big merge between 1.5 version and alpha version of 2.0.
+
+Mathieu Malaterre participated to the OpenJPEG 2.0 version and improved the libraries and utilities. 
+
+Yannick Verschueren, 
+Herve Drolon, 
+Francois-Olivier Devaux, 
+Antonin Descampe
+    improved the libraries and utilities.
+