Several changes for more reusable ppmpf tests (#13).

Some of the purposes of issue #13 in the github issue tracker for odreex are
better dealt without increasing dependency on the autotools build system that
is currently deployed by the odreex library. This however involves additional
steps like providing an assistive build tool, coded within odreex itself.

The first step towards definitely resolving #13 is to refactor tests files
in such a way as to make them easily writable (and parsable) as well as
having better header coherence. In this commit:

    *) PPMPF_TST and PPMPF_TEST_MRUN are introduced, for the scope of
       deprecating other test macros.
    *) Gradual move towards more extensive PPMPF_TST use (see seq_foldr.cc)
    *) Some fixes and additions in <odreex/ample/charseq.hh>.
    *) run_all() introduced, check class template in <odreex/ample/test.hh>.
    *) A single header <odreex/test.hh> is to deal with testing dependencies.

The PPMPF_TST macro can eventually be rewired to control macro expansion while
compiling the tests, thus making use of the delayed expansion of the macro
function it is supposed to be creating the code for testing. All tests should
be converted to using it, new tests should deploy it.
During 'make test', compiler data appears on top.
Updating ppmpf (range, nargs) tests to PPMPF_TST, range split (#13).
Merging new tests styles and examples into devbox.
More adjustments for PPMPF_TST, added assistive macros added (#13).
More ppmpf tests into distinct files, 'make tests' into 'make test' (#13).

    *) Different ppmpf macro functions for ppmpf tuples where split out of
       the single chunk used as a test.
    *) There is not distinct 'make tests' anymore, everything done from now
       on in 'make test'.
Update ppmpf sequence tests, add untracked ppmpf tuple tests (#13).
Final ppmpf sequence tests conversion to PPMPF_TST, #13.
Making PPMPF_TST default in all current ppmpf tests, resolves #13.

The introducion of USE_TEST_EXPANSION flag in the preprocessor gives the
ppmpf test macros the characteristic of expanding the macros if and only
if 'make test' is issued because it is then that the test macros are
going to be triggered into action.
Merging several changes to tests into the master branch.

Several tests have been split into distinct files, test macros expand
only when 'make test' is issued, 'make tests' functionality merged into
'make test' target. The whole format for ppmpf tests allows for easy
test generation.