Hardware meshbuffers are now deleted when they hold the last reference to a meshbuffer

HW buffers were keeping meshbuffers alive for 20000 frames even when no one else was using them anymore.
In cases of rapid creating/destroying static meshbuffers this could lead to serious memory leaks (which then kinda topped out after 5 minutes, but at that point it could already be too late).

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6599 dfc29bdd-3216-0410-991c-e03cc46cb475

changes.txt

@@ -1,6 +1,7 @@
 --------------------------
 Changes in 1.9 (not yet released)
 
+- Hardware meshbuffers are now deleted when they hold the last reference to a meshbuffer
 - Variable order inside SMaterial and SMaterialLayer changed for better packing
 - line3d::getClosestPoint can now chose between using line or line segment
 - MY3D loader deprecated and disabled by default as MY3D tools can't be found on the web anymore. Also could always be used as external loader.

source/Irrlicht/CNullDriver.cpp

@@ -1815,7 +1815,7 @@ void CNullDriver::updateAllHardwareBuffers()
 		SHWBufferLink *Link=Iterator.getNode()->getValue();
 
 		Link->LastUsed++;
-		if (Link->LastUsed>20000)
+		if (Link->LastUsed>20000 || Link->MeshBuffer->getReferenceCount() == 1)
 		{
 			deleteHardwareBuffer(Link);
 

tests/tests-last-passed-at.txt

@@ -1,4 +1,4 @@
 Tests finished. 72 tests of 72 passed.
 Compiled as DEBUG
-Test suite pass at GMT Thu Feb 22 17:49:13 2024
+Test suite pass at GMT Thu Feb 29 13:39:39 2024