Fixing stack overflow issues when slicing in SLA mode:

The BackgroundSlicingProcess thread will now have the same stack size
allocated as the TBB worker threads:
4MB on 64bit systems and 2MB on 32bit systems.

src/slic3r/GUI/BackgroundSlicingProcess.cpp

@@ -220,7 +220,11 @@ bool BackgroundSlicingProcess::start()
 	if (m_state == STATE_INITIAL) {
 		// The worker thread is not running yet. Start it.
 		assert(! m_thread.joinable());
-		m_thread = std::thread([this]{this->thread_proc_safe();});
+		boost::thread::attributes attrs;
+		// Duplicating the stack allocation size of Thread Building Block worker threads of the thread pool:
+		// allocate 4MB on a 64bit system, allocate 2MB on a 32bit system by default.
+		attrs.set_stack_size((sizeof(void*) == 4) ? (2048 * 1024) : (4096 * 1024));
+		m_thread = boost::thread(attrs, [this]{this->thread_proc_safe();});
 		// Wait until the worker thread is ready to execute the background processing task.
 		m_condition.wait(lck, [this](){ return m_state == STATE_IDLE; });
 	}

src/slic3r/GUI/BackgroundSlicingProcess.hpp

@@ -4,9 +4,9 @@
 #include <string>
 #include <condition_variable>
 #include <mutex>
-#include <thread>
 
 #include <boost/filesystem.hpp>
+#include <boost/thread.hpp>
 
 #include <wx/event.h>
 
@@ -161,7 +161,7 @@ private:
 	PrintHostJob                m_upload_job;
 	// Thread, on which the background processing is executed. The thread will always be present
 	// and ready to execute the slicing process.
-	std::thread		 			m_thread;
+	boost::thread		 		m_thread;
 	// Mutex and condition variable to synchronize m_thread with the UI thread.
 	std::mutex 		 			m_mutex;
 	std::condition_variable		m_condition;