docs: Identify examples that are C code

https://bugzilla.gnome.org/show_bug.cgi?id=723119

gdk/gdk.c

@@ -502,7 +502,7 @@ gdk_init (int *argc, char ***argv)
  *
  * A minimal main program for a threaded GTK+ application
  * looks like:
- * |[
+ * |[<!-- language="C" -->
  * int
  * main (int argc, char *argv[])
  * {
@@ -532,7 +532,7 @@ gdk_init (int *argc, char ***argv)
  *
  * Erik Mouw contributed the following code example to
  * illustrate how to use threads within GTK+ programs.
- * |[
+ * |[<!-- language="C" -->
  * /<!---->*-------------------------------------------------------------------------
  *  * Filename:      gtk-thread.c
  *  * Version:       0.99.1
@@ -843,7 +843,7 @@ gdk_threads_dispatch_free (gpointer data)
  * running in thread A and accessing @self after it has been finalized
  * in thread B:
  *
- * |[
+ * |[<!-- language="C" -->
  * static gboolean
  * idle_callback (gpointer data)
  * {
@@ -949,7 +949,7 @@ gdk_threads_add_idle (GSourceFunc    function,
  * This variant of g_timeout_add_full() can be thought of a MT-safe version 
  * for GTK+ widgets for the following use case:
  *
- * |[
+ * |[<!-- language="C" -->
  * static gboolean timeout_callback (gpointer data)
  * {
  *    SomeWidget *self = data;

gdk/gdkapplaunchcontext.c

@@ -36,7 +36,7 @@
  * screen or workspace.
  * <example>
  * <title>Launching an application</title>
- * |[
+ * |[<!-- language="C" -->
  * GdkAppLaunchContext *context;
  *
  * context = gdk_display_get_app_launch_context (display);

gdk/gdkdisplay.c

@@ -2115,7 +2115,7 @@ static GQueue gdk_error_traps = G_QUEUE_INIT;
  *
 * <example>
  * <title>Trapping an X error</title>
- * |[
+ * |[<!-- language="C" -->
  * gdk_error_trap_push (<!-- -->);
  *
  *  // ... Call the X function which may cause an error here ...

gdk/gdkdisplaymanager.c

@@ -87,7 +87,7 @@
  *
  * <example id="backend-specific">
  * <title>Backend-specific code</title>
- * |[
+ * |[<!-- language="C" -->
  * #ifdef GDK_WINDOWING_X11
  *   if (GDK_IS_X11_DISPLAY (display))
  *     {
@@ -225,7 +225,7 @@ static const gchar *allowed_backends;
  * By default, GDK tries all included backends.
  *
  * For example,
- * |[
+ * |[<!-- language="C" -->
  * gdk_set_allowed_backends ("wayland,quartz,*");
  * ]|
  * instructs GDK to try the Wayland backend first,

gdk/gdkevents.c

@@ -1676,7 +1676,7 @@ gdk_event_get_source_device (const GdkEvent *event)
  * core pointer. Coordinate extraction, processing and requesting more
  * motion events from a %GDK_MOTION_NOTIFY event usually works like this:
  *
- * |[
+ * |[<!-- language="C" -->
  * {
  *   /&ast; motion_event handler &ast;/
  *   x = motion_event->x;

gdk/gdkevents.h

@@ -1142,7 +1142,7 @@ struct _GdkEventDND {
  * The event type is always the first field in all of the event types, and
  * can always be accessed with the following code, no matter what type of
  * event it is:
- * |[
+ * |[<!-- language="C" -->
  *   GdkEvent *event;
  *   GdkEventType type;
  *
@@ -1153,14 +1153,14 @@ struct _GdkEventDND {
  * can be cast to the appropriate event type, or the union member
  * name can be used. For example if the event type is %GDK_BUTTON_PRESS
  * then the x coordinate of the button press can be accessed with:
- * |[
+ * |[<!-- language="C" -->
  *   GdkEvent *event;
  *   gdouble x;
  *
  *   x = ((GdkEventButton*)event)->x;
  * ]|
  * or:
- * |[
+ * |[<!-- language="C" -->
  *   GdkEvent *event;
  *   gdouble x;
  *

gdk/gdkkeys.c

@@ -503,7 +503,7 @@ gdk_keymap_lookup_key (GdkKeymap          *keymap,
  * <literal>&lt;Control&gt;plus</literal> accelerator &lt;Shift&gt; should
  * be masked out.
  * </para>
- * |[
+ * |[<!-- language="C" -->
  * &sol;* We want to ignore irrelevant modifiers like ScrollLock *&sol;
  * &num;define ALL_ACCELS_MASK (GDK_CONTROL_MASK | GDK_SHIFT_MASK | GDK_MOD1_MASK)
  * gdk_keymap_translate_keyboard_state (keymap, event->hardware_keycode,
@@ -518,7 +518,7 @@ gdk_keymap_lookup_key (GdkKeymap          *keymap,
  * all modifiers that might affect the translation of the key;
  * this allowed accelerators to be stored with irrelevant consumed
  * modifiers, by doing:</para>
- * |[
+ * |[<!-- language="C" -->
  * &sol;* XXX Don't do this XXX *&sol;
  * if (keyval == accel_keyval &&
  *     (event->state &amp; ~consumed &amp; ALL_ACCELS_MASK) == (accel_mods &amp; ~consumed))

gdk/gdkpango.c

@@ -53,7 +53,7 @@
  * <title>Draw transformed text with Pango and cairo</title>
  * <!-- Note that this example is basically the same as
  *      demos/gtk-demo/rotated_text.c -->
- * |[
+ * |[<!-- language="C" -->
  * #define RADIUS 100
  * #define N_WORDS 10
  * #define FONT "Sans Bold 18"

gdk/gdkwindow.h

@@ -421,7 +421,7 @@ struct _GdkWindowAttr
  * Here's an example of how the terminal example would be implemented, assuming
  * a terminal area widget called "terminal" and a toplevel window "toplevel":
  *
- * |[
+ * |[<!-- language="C" -->
  * 	GdkGeometry hints;
  *
  * 	hints.base_width = terminal->char_width;

gdk/wayland/gdkdisplay-wayland.c

@@ -49,7 +49,7 @@
  * calls by an ifdef as follows. Since GDK may be built with multiple
  * backends, you should also check for the backend that is in use (e.g. by
  * using the GDK_IS_WAYLAND_DISPLAY() macro).
- * |[
+ * |[<!-- language="C" -->
  * #ifdef GDK_WINDOWING_WAYLAND
  *   if (GDK_IS_WAYLAND_DISPLAY (display))
  *     {

gdk/wayland/gdkwindow-wayland.c

@@ -2275,7 +2275,7 @@ gdk_wayland_window_get_wl_surface (GdkWindow *window)
  * This function should be called before a #GdkWindow is shown. This is
  * best done by connecting to the #GtkWidget::realize signal:
  *
- * |[
+ * |[<!-- language="C" -->
  *   static void
  *   widget_realize_cb (GtkWidget *widget)
  *   {