[X11] Reconcile logical keyboard state with physical state on FocusIn

since the window system doesn't do it for us like other platforms.

This prevents sticky keys and missed keys when going in and out
of focus, for example Alt would appear to stick if switching away
from an SDL app with Alt-Tab and had to be pressed again.

CR: Sam

Xcode-iOS/Template/SDL iOS Application/main.c

@@ -0,0 +1,98 @@
+/*
+ *  rectangles.c
+ *  written by Holmes Futrell
+ *  use however you want
+ */
+
+#include "SDL.h"
+#include <time.h>
+
+#define SCREEN_WIDTH 320
+#define SCREEN_HEIGHT 480
+
+int
+randomInt(int min, int max)
+{
+    return min + rand() % (max - min + 1);
+}
+
+void
+render(SDL_Renderer *renderer)
+{
+
+    Uint8 r, g, b;
+
+    /* Clear the screen */
+    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
+    SDL_RenderClear(renderer);
+
+    /*  Come up with a random rectangle */
+    SDL_Rect rect;
+    rect.w = randomInt(64, 128);
+    rect.h = randomInt(64, 128);
+    rect.x = randomInt(0, SCREEN_WIDTH);
+    rect.y = randomInt(0, SCREEN_HEIGHT);
+
+    /* Come up with a random color */
+    r = randomInt(50, 255);
+    g = randomInt(50, 255);
+    b = randomInt(50, 255);
+    SDL_SetRenderDrawColor(renderer, r, g, b, 255);
+
+    /*  Fill the rectangle in the color */
+    SDL_RenderFillRect(renderer, &rect);
+
+    /* update screen */
+    SDL_RenderPresent(renderer);
+}
+
+int
+main(int argc, char *argv[])
+{
+
+    SDL_Window *window;
+    SDL_Renderer *renderer;
+    int done;
+    SDL_Event event;
+
+    /* initialize SDL */
+    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
+        printf("Could not initialize SDL\n");
+        return 1;
+    }
+
+    /* seed random number generator */
+    srand(time(NULL));
+
+    /* create window and renderer */
+    window =
+        SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,
+                         SDL_WINDOW_OPENGL);
+    if (!window) {
+        printf("Could not initialize Window\n");
+        return 1;
+    }
+
+    renderer = SDL_CreateRenderer(window, -1, 0);
+    if (!renderer) {
+        printf("Could not create renderer\n");
+        return 1;
+    }
+
+    /* Enter render loop, waiting for user to quit */
+    done = 0;
+    while (!done) {
+        while (SDL_PollEvent(&event)) {
+            if (event.type == SDL_QUIT) {
+                done = 1;
+            }
+        }
+        render(renderer);
+        SDL_Delay(1);
+    }
+
+    /* shutdown SDL */
+    SDL_Quit();
+
+    return 0;
+}