Cleanup: iif should be iff (if-and-only-if) (#11570)

src/core/geometry_type.hpp

@@ -215,7 +215,7 @@ struct Rect {
 	/**
 	 * Test if a point falls inside this Rect.
 	 * @param pt the point to test.
-	 * @return true iif the point falls inside the Rect.
+	 * @return true iff the point falls inside the Rect.
 	 */
 	inline bool Contains(const Point &pt) const
 	{

src/newgrf_object.h

@@ -78,7 +78,7 @@ struct ObjectSpec {
 
 	/**
 	 * Test if this object is enabled.
-	 * @return True iif this object is enabled.
+	 * @return True iff this object is enabled.
 	 */
 	bool IsEnabled() const { return this->views > 0; }