Remove DSTACK support (#6346)

Debugstacks is not useful, we don't really use it, the DebugStack is not pertinent, gdb and lldb are better if we really want to debug.

src/httpfetch.cpp

@@ -642,8 +642,6 @@ class CurlFetchThread : public Thread
 
 	void *run()
 	{
-		DSTACK(FUNCTION_NAME);
-
 		CurlHandlePool pool;
 
 		m_multi = curl_multi_init();