Use IOFile for TextureToPng to support non-ascii

Changed save texture/screenshot uses to std::string
Removed unneeded new/delete calls when dealing with temp data.

Source/Core/VideoBackends/Software/Src/SWRenderer.cpp

@@ -142,7 +142,7 @@ void SWRenderer::DrawTexture(u8 *texture, int width, int height)
 	if (s_bScreenshot)
 	{
 		std::lock_guard<std::mutex> lk(s_criticalScreenshot);
-		TextureToPng(texture, width*4, s_sScreenshotName.c_str(), width, height, false);
+		TextureToPng(texture, width*4, s_sScreenshotName, width, height, false);
 		// Reset settings
 		s_sScreenshotName.clear();
 		s_bScreenshot = false;