Revert "use boost::shared_ptr instead of manual ref counting"

This reverts commit 8eeb02dcc1a4bc99b083b1a591b4a70003a1604f.

Conflicts:
	include/vcl/opengl/OpenGLContext.hxx
	vcl/inc/openglgdiimpl.hxx
	vcl/opengl/gdiimpl.cxx

Change-Id: I85cc7a46876ffba5ab861f6dd83b07da466b212b