instructions: foreign features: mention programming environment

.../coding_style/no_draft_allowed.rst,
.../coding_style/use_of_foreign_features.rst: Here.

source/instructions/coding_style/no_draft_allowed.rst

@@ -12,6 +12,3 @@ In any case, *dead code and dead comments must be removed*. You are free to
 leave comments spotting places where you fixed a :code:`FIXME:` (and actually
 should in order to keep trace of what you have implemented yourself), but never
 leave a fixed :code:`FIXME:` in your code.  Nor any irrelevant comment.
-
-The official compiler for this project, is GNU C++ Compiler, |gccversion|
-or higher (see :ref:`GCC`).

source/instructions/coding_style/use_of_foreign_features.rst

@@ -13,16 +13,15 @@ approaches, and ended with unmaintainable pieces of code.
 If you *and your group* are sure you can afford some additional
 difficulty (for additional benefits), then you may use the following
 extra tools.  *You have to warn the examiners* that you use these
-tools.  You also have to take care of harnessing :code:`configure.ac` to
+tools. You also have to take care of harnessing :code:`configure.ac` to
 make sure that what you need is available on the testing environment.
 Be also aware that you are likely to obtain less help from us if you use
 tools that we don't master: You are on your own, but, hey!, that's what
 you're looking for, ain't it?
 
-Do keep in mind that we have to be able to compile your code in our testing
-environment (see :ref:`Submission`), otherwise we won't be able to grade it,
-which means you'll get a 0.
+Keep in mind that the official environment for this project is as described in
+:ref:`Programming Environment`. Not being able to build and run your project
+on this environment means we won't be able to grade you and you'll get a 0.
 
-If you have any question about such foreign features, do not hesitate to ask us.
-That being said, do keep in mind that the |project| project is not designed with
-them in mind.
+If you still have any question or proposals about such foreign features, do
+not hesitate to ask us.