Improved CMakeLists.txt

A direct port of Claus Klein's work with a minor fix to include directories.

zlib 1.2.11

zlib 1.2.10

zlib 1.2.9

zlib 1.2.8

zlib 1.2.7.3

zlib 1.2.7.2

zlib 1.2.7.1

zlib-1.2.7

zlib 1.2.6.1