Feature/preprocessor fc libc

Mise à jour des oracles suite au commit frama-c/frama-c@4f01d985 . À merger quand frama-c/frama-c!201 sera elle-même mergée dans le noyau.

See merge request !6

[translation] add a missing cast when an integer is used in a floating point/real context (was revealed by a Value's change, and now reveals a bug with == over reals)

[tests] update oracles according to various recent kernel changes

Bug/bts1831 (argc / argv)

Implements 1831

 - fix indentation
 - follow the model of must_init, build_initializer
 - only generated code if generate is set,
 - generate code "on project".
 - rename mainargs.i -> mainargs.c