LIMIT hid an off-by-one bug when tests used end iterators. We rename the
assertion to uncover all uses of the flawed implementation, and split it
into an identical assertion, and one intended to protect against
iterator ends.
GCC produces ODR error when including paths of the form './foo' and
'foo' in the same binary. Rather than managing duplication we just
universally pick the absolute form over the relative form.
