Fix build: missing boost_headers

Change-Id: I84a006d69a2ddf58fcd6d30f6e82a66a91c07456
Remove unused OpenGLContext struct

Change-Id: I4a619794f42bfc13c5685899c81f21aff68a9b5e
Fix build: namespace in wrong place.

Change-Id: I1c13e8932b3b95267470963c2b64bb98026749dd
Define dllapi for vclopengl

Change-Id: I0815dbf9f580e8fa092ebf485a60df61e2fdf15a