Fix regression due to GlueGen commit c3054a01990e55ab35756ea23ab7d7c05f24dd37, completes JOGL commit 68ca3ae8fcce28c62034299bc6e6f7eaab50bd1f

Add handling of 'initializeImpl()' of generated GLU* classes:
  - GLU      : no 'initializeImpl()' <- no libs
  - GLUgl2es1: no 'initializeImpl()' <- no libs
  - GLUgl:     call 'initializeImpl()' in manual static init impl.

Further more, we shall not initialize the GLU* classes in GLU
static init method, querying GLU* class availability.

Tested via OlympicES1.