Add DrawPoint3D() function to models.c (#1019)

Uses fewer vertexes than using DrawCube() or DrawSphere() for points.  The small line is on analogy to the code for DrawPoint() in shapes.c.

src/models.c

@@ -110,6 +110,22 @@ void DrawLine3D(Vector3 startPos, Vector3 endPos, Color color)
     rlEnd();
 }
 
+//Draw a point in 3D space--actually a small line.
+void DrawPoint3D(Vector3 pos, Color color) {
+
+    if (rlCheckBufferLimit(8)) rlglDraw();
+    rlPushMatrix();
+    rlTranslatef(pos.x,pos.y,pos.z);
+    rlBegin(RL_LINES);
+        rlColor4ub(color.r, color.g, color.b, color.a);
+        rlVertex3f(0.0,0.0,0.0);
+        rlVertex3f(0.0,0.0,0.1);
+    rlEnd();
+    rlPopMatrix();
+
+return;
+}
+
 // Draw a circle in 3D world space
 void DrawCircle3D(Vector3 center, float radius, Vector3 rotationAxis, float rotationAngle, Color color)
 {