[poincare] Enable interrupting some methods in Simplify that are called

recursively

Change-Id: I5b8c0de51617a3a36b3c8bc673de66dc60e74483

poincare/src/expression.cpp

@@ -168,9 +168,15 @@ bool Expression::IsMatrix(const Expression * e) {
 int Expression::SimplificationOrder(const Expression * e1, const Expression * e2) {
   if (e1->type() > e2->type()) {
     return -(e2->simplificationOrderGreaterType(e1));
+    if (shouldStopProcessing()) {
+      return 1;
+    }
   } else if (e1->type() == e2->type()) {
     return e1->simplificationOrderSameType(e2);
   } else {
+    if (shouldStopProcessing()) {
+      return -1;
+    }
     return e1->simplificationOrderGreaterType(e2);
   }
 }

poincare/src/power.cpp

@@ -34,6 +34,9 @@ Expression * Power::clone() const {
 }
 
 Expression::Sign Power::sign() const {
+  if (shouldStopProcessing()) {
+    return Sign::Unknown;
+  }
   if (operand(0)->sign() == Sign::Positive && operand(1)->sign() != Sign::Unknown) {
     return Sign::Positive;
   }