gcc fixes

src/runtime/dict.cpp

@@ -104,8 +104,11 @@ Box* dictSetitem(BoxedDict* self, Box* k, Box* v) {
 void dict_dtor(BoxedDict* self) {
     self->d.clear();
 
-    // I can't believe this works:
-    (&self->d)->~decltype(self->d)();
+    // I thought, in disbelief, that this works:
+    //(&self->d)->~decltype(self->d)();
+    // but that's only on clang, so instead do this:
+    typedef decltype(self->d) T;
+    (&self->d)->~T();
 }
 
 void setupDict() {

src/runtime/types.cpp

@@ -126,7 +126,8 @@ extern "C" void tupleGCHandler(GCVisitor *v, void* p) {
     BoxedTuple *t = (BoxedTuple*)p;
     int size = t->elts.size();
     if (size) {
-        v->visitRange((void**)&t->elts[0], (void**)&t->elts[size]);
+        v->visitRange(const_cast<void**>((void const*const*)&t->elts[0]),
+                      const_cast<void**>((void const*const*)&t->elts[size]));
     }
 }