Bug 1017 - TextureIO.write(Texture, File) throws GLException Not a GL2 implementation on GL3 contexts

_gl.getGL2() -> _gl.getGL2GL3()
Bug 1052 - OpenGL ES 3.0 Mesa 10.1.3 Caught GLException: Not a GL4ES3 implementation - Part 1/2

Test enhancements triggering issue 'Bug 1052 - OpenGL ES 3.0 Mesa 10.1.3 Caught GLException: Not a GL4ES3 implementation'

- TestGLProfile01NEWT: Complete GLProfile and GL-object and GLContext validation

- On OpenGL ES 3.0 Mesa 10.1.4 it produces:

1) test06GLProfileGL4ES3(com.jogamp.opengl.test.junit.jogl.acore.TestGLProfile01NEWT)
javax.media.opengl.GLException: GL4ES3 is neither GL4bc, GL4 nor GLES3
    at com.jogamp.opengl.test.junit.jogl.acore.TestGLProfile01NEWT.validateGLProfileGL4ES3(TestGLProfile01NEWT.java:531)
    at com.jogamp.opengl.test.junit.jogl.acore.TestGLProfile01NEWT.validateOffline(TestGLProfile01NEWT.java:708)
    at com.jogamp.opengl.test.junit.jogl.acore.TestGLProfile01NEWT.test06GLProfileGL4ES3(TestGLProfile01NEWT.java:948)

i.e. wrong mapping of request GL4ES3 -> GL3