Further abstracting zip / zipwith 'get', 'pop' metaconstruct mechanics.
Further abstraction of zip / zipwith mechanics for 'empty' check.
Refactored <odreex/ppmpf/algorithms/zipaux.hh>

Given the introduction of more abstract metaconstructs for zip / zipwith high
function macros, there was some boilerplate removed from the zip related
headers. This is also preparation for implementing zip / zipwith for ppmpf
sequences.
Prototype for ppmpf sequence zip (version for 2 sequences).

Given two ppmpf sequences s1 = (a)(b)(c)..., and s2 = (1)(2)(3)... then the
ppmpf zip function is defined as:

    PPMPF_SEQ_ZIP(s1,s2) -> ((a)(1))((b)(2))((c)(3))...
    PPMPF_SEQ_ZIP((),()) -> (()())
    PPMPF_SEQ_ZIP(,)     -> /* nothing */
Completed ppmpf sequences zip for 2 to 9 sequences.
Added zipwith implementation for ppmpf sequences.
Added tests for zipping ppmpf sequences.
Tests for zip and zipwith for ppmpf sequences ranging 2 - 6.
Completed tests for zipping ppmpf tuples, other fixes.
Tests for zipping ppmpf sequences now range 2 - 9.
Tests for zipwith'ing ppmpf sequences now range 2 - 9.
Making zip / zipwith fully operational, resolves #4.