vidjil.cpp: Don't use exit()

See 1a7bb7f8 for reason why.

Fix (in part?) #3771

algo/tests/should-get-tests/00-clean-memory-on-exit.should-get

@@ -9,4 +9,4 @@ $ Two times for the definition
 1:add_flag.*__only_on_exit__clean_memory
 
 $ And two other times, just before exiting
-2:if .__only_on_exit__clean_memory. .* exit.0.
+2:if .__only_on_exit__clean_memory. .* return.0.

algo/vidjil.cpp

@@ -983,7 +983,7 @@ int main (int argc, char **argv)
 	  cout << "     " << key << " " << it->second.name << endl ;
 	}
       
-      if (__only_on_exit__clean_memory) { delete multigermline; } exit(0);
+      if (__only_on_exit__clean_memory) { delete multigermline; } return 0;
     }
 
 
@@ -1654,7 +1654,7 @@ int main (int argc, char **argv)
   outputVidjil->out(out_json);
 
   //$$ Clean
-  if (__only_on_exit__clean_memory) { delete multigermline ; delete reads; } exit(0) ;
+  if (__only_on_exit__clean_memory) { delete multigermline ; delete reads; } return 0 ;
 }
 
 //$$ end