Undef sprintf if it exists before trying to define it.
Mac OSX 10.9 with xcode 6.1 / llvm 3.5 defines it here: /usr/include/secure/_stdio.h


git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@28143 f0d54148-0727-0410-94bb-9a71ac55c965