remove empty destructors so waypoints can be moved

A user-declared destructor, even an empty one, suppresses the implicit
move operations, so waypoint and waypoint_list were silently copy-only:
every Waypoint_lists erase, insert, and reallocation deep-copied entire
lists, and inserting a waypoint mid-path copied every shifted waypoint.
Removing the destructors restores the implicit moves (correct and
noexcept, since the members are vec3d/int and SCP_vector/SCP_string),
turning those shifts into pointer steals.  The implicit deep copies
remain available and unchanged.  Waypoint identity is index-encoded in
Objects[].instance and renumbered on insert/erase, so relocation
semantics are unaffected.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Goober5000

code/object/waypoint.cpp

@@ -38,11 +38,6 @@ waypoint::waypoint(const vec3d *position)
 	this->m_objnum = -1;
 }
 
-waypoint::~waypoint()
-{
-	// nothing to do
-}
-
 const vec3d *waypoint::get_pos() const
 {
 	if (m_objnum >= 0)
@@ -118,11 +113,6 @@ waypoint_list::waypoint_list(const char *name)
 	this->m_color_r = this->m_color_g = this->m_color_b = 255;
 }
 
-waypoint_list::~waypoint_list()
-{
-	// nothing to do
-}
-
 const char *waypoint_list::get_name() const
 {
 	return m_name;

code/object/waypoint.h

@@ -12,7 +12,6 @@ class waypoint
 	public:
 		waypoint();
 		waypoint(const vec3d *pos);
-		~waypoint();
 
 		// accessors
 		const vec3d *get_pos() const;
@@ -37,7 +36,6 @@ class waypoint_list
 	public:
 		waypoint_list();
 		waypoint_list(const char *name);
-		~waypoint_list();
 
 		// accessors
 		const char *get_name() const;