Support for using common ZLib shared library

[cher-nov]

Currently Vampyre uses its own local reimplementation of ZLib in Delphi:
https://github.com/galfar/imaginglib/tree/f6ef092b/Source/ZLib
https://github.com/galfar/imaginglib/blob/f6ef092b/Extensions/LibTiff/ZLibDelphi.pas

It would be great if there was an option to use the regular libzlib instead, since it may already be used in the final project. This would reduce the code size noticeably.