OGR VRT: add example provided by Jukka

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@26034 f0d54148-0727-0410-94bb-9a71ac55c965
Add vsipreload.cpp that can be compiled as a shared library that can be LD_PRELOAD'ed as an overload of libc to enable VSI Virtual FILE API to be used with binaries using regular libc for I/O

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@26035 f0d54148-0727-0410-94bb-9a71ac55c965