volk: fix CentOS build failure with extra lib64 in path

Use updated GrBoost.cmake from main build
wxgui: Fixes to solve issues using GL sinks on OS X
plotter/plotter_base.py: Create explicit OpenGL context, check if window is shown before realising context & only create PaintDC is paint triggered by WM message (OS paint event)
Added SetSizeHints to WX sink windows so sizing occurs correctly
blocks: fix file meta data source to handle repeat of files.