Modified src/CMakeLists.txt so that the paths to ZLIB are not hardcoded on...

Modified src/CMakeLists.txt so that the paths to ZLIB are not hardcoded on Windows and instead set the variable 'ZLIB_ROOT' used by the FindZLIB module in CMake.  Modified the (older) build scripts for windows so that they set ZLIB_ROOT as a parameter to the 'cmake' command.  In addition, the variable WORKBENCH_FREETYPE_DIR has been added to specify the path to the FreeType root directory.  If this variable is present, it is used by CMake to set the environment variable FREETYPE_DIR used in the CMake module FindFreeType.  Lastly, added CMake Policy CMP0020 to CMakeLists.txt for Windows only to eliminate many warnings produced by newer versions of CMake.