Math/Point2D, GDI/Point: add operator-
OpenGL/Triangulate: use operator-
OpenGL/Triangulate: use "auto"
TopographyFile: move code to LoadShape()
TopographyFile: use "zzip_dir" without "struct"
TopographyFile: make a few attributes "const"
TopographyFile: don't use NonCopyable
TopographyFile: check the msShapefileWhichShapes() return value
Topography/XShape: update projection code comment

See commit 1d0d2ccc
zzip: add zzip_pread() prototype
zzip: implement zzip_pread() using pread()
Topography/shapelib: use zzip_pread()

Speeds up the topography loader by 20%.
OpenGL/Buffer: disable the copy constructor