First step of moving to libuv-0.10.12.

1. libuv updated to 0.10.12
2. External cares submodule was added
3. CMake files for libuv and cares were initially added.

@note Build is broken.
Second step of moving to libuv-0.10.12.

Compilation was fixed. But cares from old version of libuv have to be reintegrated into
luvit directly to provide properly work. There is freeze on luvit exit now.

@note Luvit doesn't work yet - freeze on exit.