Merge pull request #409 from pah/fix/biginteger-self-assign

BigInteger: guard against self-assignment

include/rapidjson/internal/biginteger.h

@@ -54,8 +54,10 @@ public:
     
     BigInteger& operator=(const BigInteger &rhs)
     {
+        if (this != &rhs) {
             count_ = rhs.count_;
             std::memcpy(digits_, rhs.digits_, count_ * sizeof(Type));
+        }
         return *this;
     }