Fix resizing on linux

.vscode/c_cpp_properties.json

             "cStandard": "c11",
             "cppStandard": "c++17",
             "intelliSenseMode": "gcc-x64"
+        },
+        {
+            "name": "Linux",
+            "includePath": [
+                "${workspaceFolder}/**"
+            ],
+            "defines": [],
+            "compilerPath": "/usr/bin/gcc",
+            "cStandard": "c11",
+            "cppStandard": "c++17",
+            "intelliSenseMode": "gcc-x64"
         }
     ],
     "version": 4

include/olcPixelGameEngine.h

 
 	Author
 	~~~~~~
-	David Barr, aka javidx9, �OneLoneCoder 2018, 2019
+	David Barr, aka javidx9, ©OneLoneCoder 2018, 2019
 */
 
 //////////////////////////////////////////////////////////////////////////////////////////
 		XVisualInfo*            olc_VisualInfo;
 		Colormap                olc_ColourMap;
 		XSetWindowAttributes    olc_SetWindowAttribs;
+		XSizeHints			    olc_SizeHints;
 		Display*				olc_WindowCreate();
 #endif
 

src/olcPixelGameEngine.cpp

 			nWindowWidth = gwa.width;
 			nWindowHeight = gwa.height;
 			olc_UpdateViewport();
+		} else {
+			olc_SizeHints.flags = PMaxSize | PMinSize;
+			olc_SizeHints.max_width = nScreenWidth * nPixelWidth;
+			olc_SizeHints.max_height = nScreenHeight * nPixelHeight;
+			olc_SizeHints.min_width = nScreenWidth * nPixelWidth;
+			olc_SizeHints.min_height = nScreenHeight * nPixelHeight;
+
+			XSetWMNormalHints(olc_Display, olc_Window, &olc_SizeHints);
 		}
 
 		// Create Keyboard Mapping