Fixed warnings from Clang static analysis.

examples/heightmap.c

@@ -644,7 +644,7 @@ int main(int argc, char** argv)
     /* main loop */
     frame = 0;
     iter = 0;
-    dt = last_update_time = glfwGetTime();
+    last_update_time = glfwGetTime();
 
     while (!glfwWindowShouldClose(window))
     {

tests/glfwinfo.c

@@ -253,9 +253,6 @@ int main(int argc, char** argv)
         }
     }
 
-    argc -= optind;
-    argv += optind;
-
     // Initialize GLFW and create window
 
     if (!valid_version())

tests/modes.c

@@ -218,9 +218,6 @@ int main(int argc, char** argv)
         }
     }
 
-    argc -= optind;
-    argv += optind;
-
     glfwSetErrorCallback(error_callback);
 
     if (!glfwInit())