Evenint case study

Adds an evenint case study (from the tutorial) with some additional fun variations to the case studies.

Also change the build order in the Makefile a bit, in order to first generate all the Coq files and then run Coq in parallel on all of them.

case_studies/evenint/output/evenint/proofs/proof_EvenInt_add.v

+From caesium Require Import lang notation.
+From refinedrust Require Import typing shims.
+From refinedrust.examples.evenint.generated Require Import generated_code_evenint generated_specs_evenint generated_template_EvenInt_add.
+
+Set Default Proof Using "Type".
+
+Section proof.
+Context `{!refinedrustGS Σ}.
+
+Lemma EvenInt_add_proof (π : thread_id) :
+  EvenInt_add_lemma π.
+Proof.
+  EvenInt_add_prelude.
+
+  repeat liRStep; liShow.
+
+  all: print_remaining_goal.
+  Unshelve. all: sidecond_solver.
+  Unshelve. all: sidecond_hammer.
+  Unshelve. all: print_remaining_sidecond.
+Qed.
+End proof.