Primitives: added Cube::solidStrip().

Took me more than year of procrastination until someone finally
completely figured it out for me. Thanks y'all.

src/Magnum/Primitives/Cube.cpp

@@ -102,6 +102,48 @@ Trade::MeshData3D Cube::solid() {
     }}, {});
 }
 
+Trade::MeshData3D Cube::solidStrip() {
+    /* Sources:
+        https://twitter.com/Donzanoid/status/436843034966507520
+        http://www.asmcommunity.net/forums/topic/?id=6284#post-45209
+        https://gist.github.com/cdwfs/2cab675b333632d940cf
+
+        0---2---3---1
+        |E /|\ A|H /|
+        | / | \ | / |
+        |/ D|B \|/ I|
+        4---7---6---5
+            |C /|
+            | / |
+            |/ J|
+            4---5
+            |\ K|
+            | \ |
+            |L \|
+            0---1
+            |\ G|
+            | \ |
+            |F \|
+            2---3
+    */
+    return Trade::MeshData3D(MeshPrimitive::TriangleStrip, {}, {{
+        { 1.0f,  1.0f,  1.0f}, /* 3 */
+        {-1.0f,  1.0f,  1.0f}, /* 2 */
+        { 1.0f, -1.0f,  1.0f}, /* 6 */
+        {-1.0f, -1.0f,  1.0f}, /* 7 */
+        {-1.0f, -1.0f, -1.0f}, /* 4 */
+        {-1.0f,  1.0f,  1.0f}, /* 2 */
+        {-1.0f,  1.0f, -1.0f}, /* 0 */
+        { 1.0f,  1.0f,  1.0f}, /* 3 */
+        { 1.0f,  1.0f, -1.0f}, /* 1 */
+        { 1.0f, -1.0f,  1.0f}, /* 6 */
+        { 1.0f, -1.0f, -1.0f}, /* 5 */
+        {-1.0f, -1.0f, -1.0f}, /* 4 */
+        { 1.0f,  1.0f, -1.0f}, /* 1 */
+        {-1.0f,  1.0f, -1.0f}  /* 0 */
+    }}, {}, {});
+}
+
 Trade::MeshData3D Cube::wireframe() {
     return Trade::MeshData3D(MeshPrimitive::Lines, {
         0, 1, 1, 2, 2, 3, 3, 0, /* +Z */

src/Magnum/Primitives/Cube.h

@@ -48,6 +48,14 @@ class MAGNUM_PRIMITIVES_EXPORT Cube {
          */
         static Trade::MeshData3D solid();
 
+        /**
+         * @brief Solid cube as a single strip
+         *
+         * Non-indexed @ref MeshPrimitive::TriangleStrip. Just positions, no
+         * normals or anything else.
+         */
+        static Trade::MeshData3D solidStrip();
+
         /**
          * @brief Wireframe cube
          *