Build with jdk-11

Index: platform_build/build-generator.xml
--- platform_build/build-generator.xml.orig
+++ platform_build/build-generator.xml
@@ -32,7 +32,7 @@
 		</javac>
 
 		<!-- Compile helper classes used by the templates -->
-        <javac debug="yes" srcdir="${lwjgl.src}/java/" destdir="${lwjgl.bin}" source="1.5" target="1.5" taskname="generator">
+        <javac debug="yes" srcdir="${lwjgl.src}/java/" destdir="${lwjgl.bin}" source="1.6" target="1.6" taskname="generator">
             <include name="org/lwjgl/PointerWrapper.java"/>
             <include name="org/lwjgl/PointerBuffer.java"/>
             <!-- OpenGL -->
