mp_image: add force_window field

It's useful for some VOs (dmabuf-wayland) to know if the image params
are actually real or fake ones sent by the core for the purpose of
force_window.

player/playloop.c

@@ -1034,6 +1034,7 @@ int handle_force_window(struct MPContext *mpctx, bool force)
             .imgfmt = config_format,
             .w = w,   .h = h,
             .p_w = 1, .p_h = 1,
+            .force_window = true,
         };
         if (vo_reconfig(vo, &p) < 0)
             goto err;

video/mp_image.c

@@ -835,6 +835,7 @@ bool mp_image_params_equal(const struct mp_image_params *p1,
            p1->hw_subfmt == p2->hw_subfmt &&
            p1->w == p2->w && p1->h == p2->h &&
            p1->p_w == p2->p_w && p1->p_h == p2->p_h &&
+           p1->force_window == p2->force_window &&
            mp_colorspace_equal(p1->color, p2->color) &&
            p1->chroma_location == p2->chroma_location &&
            p1->rotate == p2->rotate &&

video/mp_image.h

@@ -46,6 +46,7 @@ struct mp_image_params {
     enum mp_imgfmt hw_subfmt;   // underlying format for some hwaccel pixfmts
     int w, h;                   // image dimensions
     int p_w, p_h;               // define pixel aspect ratio (undefined: 0/0)
+    bool force_window;          // fake image created by handle_force_window
     struct mp_colorspace color;
     enum mp_chroma_location chroma_location;
     // The image should be rotated clockwise (0-359 degrees).