restrict on static pointers
one last refinement of const use
minor change to binary tree printing
update doxygen file to include and exclude files properly
account for null test suite
forgot sizeof is compile-time so:
    remove null check of test_list since sizeof test_list[0] is *not* a null dereference even when test_list is NULL
    extend invalid suite check to account for null test_list since count is no longer zero in this case
    fix unit tests and improve documentation
this fixes a -Waddress warning that is annoying and useless
fix typos in documentation
remove file paths from doxygen documentation
add makefile details and mention gcc testing
update example output
add make file