message: Removed redundant overloading in stopping_status
  Removed redundant member functions `operator==` and `operator!=`
  in stopping_status, which were also present as `friend` functions.
diff: @@ -52,28 +52,6 @@ class stopping_status {
  const stopping_status &x, const stopping_status &y) noexcept;
  public:
  - /**
  - * Check if two stopping_status are identical
  - * @param other stopping_status to compare against
  - * @return true if and only if `*this == other`
  - */
  - GKO_ATTRIBUTES GKO_INLINE bool operator==(
  - const stopping_status &other) const noexcept
  - {
  - return data_ == other.data_;
  - }
  -
  - /**
  - * Check if two stopping_status are different
  - * @param other stopping_status to compare against
  - * @return true if and only if `*this != other`
  - */
  - GKO_ATTRIBUTES GKO_INLINE bool operator!=(
  - const stopping_status &other) const noexcept
  - {
  - return data_ != other.data_;
  - }
  -
  /**
  * Check if any stopping criteria was fulfilled.
  * @return Returns true if any stopping criteria was fulfilled.
  