Add missing headers for gcc

src/ZoneWriting/Game/IW4/ZoneWriterFactoryIW4.cpp

@@ -1,6 +1,7 @@
 #include "ZoneWriterFactoryIW4.h"
 
 #include <cassert>
+#include <cstring>
 
 #include "ContentWriterIW4.h"
 #include "Utils/ICapturedDataProvider.h"

src/ZoneWriting/Game/T6/ZoneWriterFactoryT6.cpp

@@ -1,6 +1,7 @@
 #include "ZoneWriterFactoryT6.h"
 
 #include <cassert>
+#include <cstring>
 
 #include "ContentWriterT6.h"
 #include "Utils/ICapturedDataProvider.h"

src/ZoneWriting/Writing/Processor/OutputProcessorXChunks.cpp

@@ -1,6 +1,7 @@
 #include "OutputProcessorXChunks.h"
 
 #include <cassert>
+#include <cstring>
 
 #include "Writing/WritingException.h"
 #include "Zone/ZoneTypes.h"

src/ZoneWriting/Zone/Stream/Impl/InMemoryZoneOutputStream.cpp

@@ -1,6 +1,7 @@
 #include "InMemoryZoneOutputStream.h"
 
 #include <cassert>
+#include <cstring>
 
 InMemoryZoneOutputStream::InMemoryZoneOutputStream(InMemoryZoneData* zoneData, std::vector<XBlock*> blocks, const int blockBitCount, const block_t insertBlock)
     : m_zone_data(zoneData),