Add patch to set source to 1.8

debian/patches/series

 update_classpath.patch
+set_source_1_8.patch
 URLClassLoader.patch

debian/patches/set_source_1_8.patch

+From: Dominik Stadler <dominik.stadler@gmx.at>
+Date: Tue, 26 Mar 2019 19:20:22 +0100
+Subject: set_source_1.8
+
+---
+Index: netlib-java/nbproject/project.properties
+===================================================================
+--- netlib-java.orig/nbproject/project.properties
++++ netlib-java/nbproject/project.properties
+@@ -28,8 +28,8 @@ javac.classpath=\
+ # Space-separated list of extra javac options
+ javac.compilerargs=
+ javac.deprecation=false
+-javac.source=1.5
+-javac.target=1.5
++javac.source=1.8
++javac.target=1.8
+ javac.test.classpath=\
+     ${javac.classpath}:\
+     ${build.classes.dir}:\