PointerCoordinates plugin: uninitialized members
added comment for MSVC2012 builders
Reverted commit 6589 "Disabling planetary shadows for now."
Reverted commit 6539: "solar system shadows ported"

Even though the rendering is good, it suffers from several defects:
 - very slow, mainly because the fragment shaders loops through all the solar system objects (per pixel!)
 - uses OpenGL features not very portable without real need (GL_RGBA32F textures)
 - badly integrated (the StelPainter class should not know about planet shadows!)

This codes needs to be re-worked inn a dedicated branch, not in trunk.