Add #pragma once to Headers Without an Include Guard

src/libslic3r/Format/ModelIO.hpp

@@ -1,3 +1,5 @@
+#pragma once
+
 #include <string>
 
 namespace Slic3r {

src/libslic3r/QuadricEdgeCollapse.hpp

@@ -1,3 +1,5 @@
+#pragma once
+
 // paper: https://people.eecs.berkeley.edu/~jrs/meshpapers/GarlandHeckbert2.pdf
 // sum up: https://users.csc.calpoly.edu/~zwood/teaching/csc570/final06/jseeba/
 // inspiration: https://github.com/sp4cerat/Fast-Quadric-Mesh-Simplification

src/slic3r/GUI/InstanceCheckMac.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #import <Cocoa/Cocoa.h>
 
 @interface OtherInstanceMessageHandlerMac : NSObject

src/slic3r/GUI/PartSkipDialog.hpp

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "slic3r/GUI/wxExtensions.hpp"
 #include <map>
 #include <cstdint>

src/slic3r/GUI/RemovableDriveManagerMM.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #import <Cocoa/Cocoa.h>
 
 @interface RemovableDriveManagerMM : NSObject

src/slic3r/GUI/Widgets/TextCtrl.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #include <wx/textctrl.h>
 #include <wx/colour.h>