Changes stack internals to use more descriptive struct name.
Adds the create/destory functions for a queue.
Uses subdirectory CMakeLists.txt now.
Grrr... I need coffee.
Adds unit tests with Check.

Currently, the unit tests are a bit awkward; `make check' don't work for now.
Adds proper testing.

Turns out, `make check' is only for Autotools.