Replaced PFNGLGENERATEMIPMAPPROC with PFNGLGENERATEMIPMAPEXTPROC when loading an GL extension to allow cmgui-wx to be built on win32 in the Institute again. Tracker item 2386, https://tracker.physiomeproject.org/show_bug.cgi?id=2386
Replaced PFNGLGENERATEMIPMAPPROC with PFNGLGENERATEMIPMAPEXTPROC when loading an GL extension to allow cmgui-wx to be built on win32 in the Institute again. Tracker item 2386, https://tracker.physiomeproject.org/show_bug.cgi?id=2386

cmiss/cmgui,cmiss/cmgui