local function pointer to avoid compiler warnings related to case void*.
Moved various OSG classes across to using setGLExtensions instead of getGLExtensions,
and changed them to use typedef declarations in the headers rather than casts in
the .cpp.
Updated wrappers
handle scenes with multiple views with elements that need coordinating on a per view basis.
Added beginings of new osgText::FadeText class (not functionality yet).
Note, this required adding a unsigned int context ID to the osg::isGLUExtensionSupported(,)
and osg::isGLExtensionSupported(,) functions. This may require reimplementation
of end user code to accomodate the new calling convention.
