zlib 1.2.11.
Files not required by OpenMPT have been removed.
OpenMPT specific changes:
 *  iowin32.c has been modified to only use Windows 8 WinRT API when actually
    compiling for Windows 8 or later.
 *  All custom modifications are marked with // OpenMPT
 *  For building, premake is used to generate Visual Studio project files.
    See ../build/premake/ for details.
No further changes have been made.