message: Added missing time operators. GH# 1022
diff: @@ -62,6 +62,7 @@ namespace fc {
  time_point& operator += ( const microseconds& m) { elapsed+=m; return *this; }
  time_point& operator -= ( const microseconds& m) { elapsed-=m; return *this; }
  time_point operator + (const microseconds& m) const { return time_point(elapsed+m); }
  + time_point operator + (const time_point& m) const { return time_point(elapsed+m.elapsed); }
  time_point operator - (const microseconds& m) const { return time_point(elapsed-m); }
  microseconds operator - (const time_point& m) const { return microseconds(elapsed.count() - m.elapsed.count()); }
  private:
  @@ -102,8 +103,10 @@ namespace fc {
  friend bool operator != ( const time_point_sec& a, const time_point_sec& b ) { return a.utc_seconds != b.utc_seconds; }
  time_point_sec& operator += ( uint32_t m ) { utc_seconds+=m; return *this; }
  time_point_sec& operator += ( microseconds m ) { utc_seconds+=m.to_seconds(); return *this; }
  + time_point_sec& operator += ( time_point_sec m ) { utc_seconds+=m.utc_seconds; return *this; }
  time_point_sec& operator -= ( uint32_t m ) { utc_seconds-=m; return *this; }
  time_point_sec& operator -= ( microseconds m ) { utc_seconds-=m.to_seconds(); return *this; }
  + time_point_sec& operator -= ( time_point_sec m ) { utc_seconds-=m.utc_seconds; return *this; }
  time_point_sec operator +( uint32_t offset )const { return time_point_sec(utc_seconds + offset); }
  time_point_sec operator -( uint32_t offset )const { return time_point_sec(utc_seconds - offset); }
  