A fix for picking combined with depth peeling
A fix for picking combined with depth peeling and some cleanup. Picking (not using a hardware picker) was not clearing the LastRenderingUsedDepth peelign flag and that was causing issues. Switched to that that flag is not sued but instead the information objects are used. Fix old style prop picking without hardware selector. Fix missing mtime check on OpenGLPolyDataMapper2D.
Retrieved from Merge Request #706 by Ken Martin