Don't #define snprintf _snprintf for VS2015 / VC 14.00 builds

git-svn-id: https://svn.osgeo.org/gdal/trunk@28024 f0d54148-0727-0410-94bb-9a71ac55c965
Fix a few warnings of method argument hiding member variable

git-svn-id: https://svn.osgeo.org/gdal/trunk@28025 f0d54148-0727-0410-94bb-9a71ac55c965