Add rcNew/rcDelete, template functions that allocate/deallocate objec…

…ts using rcAlloc/rcFree. (recastnavigation#324)

Add rcNew/rcDelete, template functions that allocate/deallocate objects using rcAlloc/rcNew.
The intention is to use these to move construction logic out of rcAllocateFooObject/rcFreeFooObject and into constructors/destructors, giving users flexbility in how objects are allocated. In particular, this allows stack allocation.

Recast/Include/Recast.h

@@ -332,6 +332,8 @@ struct rcCompactSpan
 /// @ingroup recast
 struct rcCompactHeightfield
 {
+	rcCompactHeightfield();
+	~rcCompactHeightfield();
 	int width;					///< The width of the heightfield. (Along the x-axis in cell units.)
 	int height;					///< The height of the heightfield. (Along the z-axis in cell units.)
 	int spanCount;				///< The number of spans in the heightfield.

Recast/Source/Recast.cpp

@@ -23,11 +23,34 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdarg.h>
-#include <new>
 #include "Recast.h"
 #include "RecastAlloc.h"
 #include "RecastAssert.h"
 
+namespace
+{
+/// Allocates and constructs an object of the given type, returning a pointer.
+/// TODO: Support constructor args.
+/// @param[in]		hint	Hint to the allocator.
+template <typename T>
+T* rcNew(rcAllocHint hint) {
+	T* ptr = (T*)rcAlloc(sizeof(T), hint);
+	::new(rcNewTag(), (void*)ptr) T();
+	return ptr;
+}
+
+/// Destroys and frees an object allocated with rcNew.
+/// @param[in]     ptr    The object pointer to delete.
+template <typename T>
+void rcDelete(T* ptr) {
+	if (ptr) {
+		ptr->~T();
+		rcFree((void*)ptr);
+	}
+}
+}  // namespace
+
+
 float rcSqrt(float x)
 {
 	return sqrtf(x);
@@ -73,7 +96,7 @@ void rcContext::log(const rcLogCategory category, const char* format, ...)
 
 rcHeightfield* rcAllocHeightfield()
 {
-	return new (rcAlloc(sizeof(rcHeightfield), RC_ALLOC_PERM)) rcHeightfield;
+	return rcNew<rcHeightfield>(RC_ALLOC_PERM);
 }
 
 rcHeightfield::rcHeightfield()
@@ -104,26 +127,44 @@ rcHeightfield::~rcHeightfield()
 
 void rcFreeHeightField(rcHeightfield* hf)
 {
-	if (!hf) return;
-	hf->~rcHeightfield();
-	rcFree(hf);
+	rcDelete(hf);
 }
 
 rcCompactHeightfield* rcAllocCompactHeightfield()
 {
-	rcCompactHeightfield* chf = (rcCompactHeightfield*)rcAlloc(sizeof(rcCompactHeightfield), RC_ALLOC_PERM);
-	memset(chf, 0, sizeof(rcCompactHeightfield));
-	return chf;
+	return rcNew<rcCompactHeightfield>(RC_ALLOC_PERM);
 }
 
 void rcFreeCompactHeightfield(rcCompactHeightfield* chf)
 {
-	if (!chf) return;
-	rcFree(chf->cells);
-	rcFree(chf->spans);
-	rcFree(chf->dist);
-	rcFree(chf->areas);
-	rcFree(chf);
+	rcDelete(chf);
+}
+
+rcCompactHeightfield::rcCompactHeightfield()
+	: width(0),
+	height(0),
+	spanCount(0),
+	walkableHeight(0),
+	walkableClimb(0),
+	borderSize(0),
+	maxDistance(0),
+	maxRegions(0),
+	bmin(),
+	bmax(),
+	cs(0),
+	ch(0),
+	cells(0),
+	spans(0),
+	dist(0),
+	areas(0)
+{
+}
+rcCompactHeightfield::~rcCompactHeightfield()
+{
+	rcFree(cells);
+	rcFree(spans);
+	rcFree(dist);
+	rcFree(areas);
 }
 
 rcHeightfieldLayerSet* rcAllocHeightfieldLayerSet()