planner: add != operator

Problem: `planner` equality testing needs a convenience != operator.

Add a `planner` `!=` operator.

Author: milroy

resource/planner/c++/planner.cpp

@@ -163,6 +163,11 @@ bool planner::operator== (const planner &o) const
     return true;
 }
 
+bool planner::operator!= (const planner &o) const
+{
+    return !operator == (o);
+}
+
 planner::~planner ()
 {
     // Destructor is nothrow

resource/planner/c++/planner.hpp

@@ -45,6 +45,7 @@ class planner {
     planner (const planner &o);
     planner &operator= (const planner &o);
     bool operator== (const planner &o) const;
+    bool operator!= (const planner &o) const;
     ~planner ();
     // Public class utilities
     int erase ();