fix(gui): explicitly set GLSL profile in shaders

src/gui/res/shaders/mdl.vert

@@ -1,4 +1,4 @@
-#version 150
+#version 150 core
 
 attribute vec3 vPos;
 attribute vec3 vNormal;

src/gui/res/shaders/mdl_shaded_textured.frag

@@ -1,4 +1,4 @@
-#version 150
+#version 150 core
 
 uniform sampler2D uMeshTexture;
 uniform sampler2D uMatCapTexture;

src/gui/res/shaders/mdl_shaded_untextured.frag

@@ -1,4 +1,4 @@
-#version 150
+#version 150 core
 
 uniform sampler2D uMeshTexture;
 uniform sampler2D uMatCapTexture;

src/gui/res/shaders/mdl_unshaded_textured.frag

@@ -1,4 +1,4 @@
-#version 150
+#version 150 core
 
 uniform sampler2D uMeshTexture;
 uniform sampler2D uMatCapTexture;

src/gui/res/shaders/mdl_wireframe.frag

@@ -1,4 +1,4 @@
-#version 150
+#version 150 core
 
 uniform sampler2D uMeshTexture;
 uniform sampler2D uMatCapTexture;