[tests] Compare the generated code just after running Value. Use gcc_x86_64 as machdep for all these tests.
[tests] call testrun.sh in test_config in order to compile and run the generated code. This code is no more the one being compared with the oracle (see above item).

[e-acsl] tests now independent of GMP version (but GMP still required)

[e-acsl] all tests are now executed with gcc
[e-acsl] fix bug with integer division and modulo
[e-acsl] untested support of most logic labels
[e-acsl]

[e-acsl] support of field accesses in logic
[e-acsl] support of array accesses (yet missing guards) in logic
[e-acsl] support of pointer dereferences (yet missing guards) in logic
[e-acsl] support of \null in logic

[e-acsl] fixed bug for negative modulos
[e-acsl] full reimplementation of environments (only one now, and it is persistent)
[e-acsl] support of lazy operators &&, || and ==>
[e-acsl] tests now execute the generated C code and check that no runtime assertion is raised

[e-acsl] Makefile's target 'install'
[e-acsl] test GMP linkage in non-regression suite ('make tests' now requires GMP >= 4.3.2)
[e-acsl] fixed bugs of GMP compatibility

- improve efficiency of mpz_clear generation
- don't run cast.i anymore (waiting for fixing issue #744)
- refactoring generation of new variables with their related stmts