Add initial support for GCJ gij JRE

gij -cp jogl-all.jar:gluegen-rt.jar com.jogamp.opengl.JoglVersion
gij -cp jogl-all.jar:gluegen-rt.jar:jogl-test.jar:junit.jar com.jogamp.opengl.test.junit.jogl.demos.es1.newt.TestRedSquareES1NEWT -width 1980 -height 1080 -time 40000

* Buffer.isDirect() operation is undefined w/ Eclipse ecj and GCJ gij JRE. …

Fix for the runtime error using GCJ gij JRE:
java.lang.NoSuchMethodError: method java.nio.Buffer.isDirect with signature ()Z was not found.
at com.jogamp.common.nio.Buffers.isDirect(Buffers.java:363)

Also Eclipse ecj refuses to compile code using java.nio.Buffer.isDirect().
```text
----------
1. ERROR
...
        return ((Buffer) buf).isDirect();
	                      ^^^^^^^^
The method isDirect() is undefined for the type Buffer
```

* The question is do we want to support JRE using Java 1.5 nio classpath implementation?