This allows the updater to work on older Windows XP systems
without the VC++ 2008 runtime redistributable installed.
* Add statically linked pre-built versions of the zlib and
bzip2 libraries.
This increases the size of the updater executable by 200KB
to ~400KB on Windows.
The zlib build system is not integrated with the updater's build
system. Rather than write a small CMakeLists.txt for the build,
this commit just adds a pre-built version of zlib
Robert Knight