add zlib to dependency tree
properly link zlib (external)
create a mechnism with ExternalProject_Add to automatically build deps

i will be using BUILD_THIRD_PARTY_LIBRARIES=ON, so that can be passed
directly to cmake to make it build all the included dependencies
flawlessly. At least that's the idea/hope. right now it's always on
though for testing.
add enet automagic make stuff
fix linker issue with builtin enet. build chipmunk as a dep, if wanted
add protobuf dep build
add zlib to dep auto build, glad they use cmake as well

because the configure script didn't want to work properly