bindings: Do not grab pointer when executing bindings (#5755)

Grabing the pointer produces a `GrabFrozen` error in applications that
are run from key bindings. Since we don't need the pointer in such
cases, we can change the call to use ASYNC. This seems to be a
historical leftover.

I've tested locally that these still work:
- bindsym $mod+x ...
- bindsym --release $mod+x ...
- bindsym $mod+button1 ...
- bindsym --release $mod+button1 ...
- bindsym --release $mod+x exec program that grabs the keyboard
  now works (see original issue)

Even in the main branch, I actually couldn't get `import` and `xdotool`
to fail with the pointer being frozen, potentially because these
programs wait a bit for the pointer to be unfrozen like i3lock does.

This patch came up in
https://github.com/i3/i3/issues/5735#issuecomment-1781321011

I wonder why the pointer is actually grabbed.

The argument I change in `xcb_grab_key` there, is `pointer_mode`, from
https://www.x.org/releases/X11R7.7/doc/man/man3/xcb_grab_key.3.xhtml:
```
pointer_mode

One of the following values:
XCB_GRAB_MODE_SYNC

The state of the keyboard appears to freeze: No further keyboard events are generated by the server until the grabbing client issues a releasing AllowEvents request or until the keyboard grab is released.

XCB_GRAB_MODE_ASYNC

Keyboard event processing continues normally.
```

I traced via `git blame` the usage of `xcb_grab_key` throughout 14 years
of i3 development and it seems that `pointer_mode` was always set to
`XCB_GRAB_MODE_SYNC`, going all the way back to
b664456706.

Fixes #5735

docs/userguide

@@ -512,8 +512,8 @@ your bindings in the same physical location on the keyboard, use keycodes.
 If you don’t switch layouts, and want a clean and simple config file, use
 keysyms.
 
-Some tools (such as +import+ or +xdotool+) might be unable to run upon a
-KeyPress event, because the keyboard/pointer is still grabbed. For these
+Some tools (such as +xdotool+) might be unable to run upon a
+KeyPress event, because the keyboard is still grabbed. For these
 situations, the +--release+ flag can be used, which will execute the command
 after the keys have been released.
 

release-notes/changes/1-grab-pointer

@@ -0,0 +1 @@
+do not grab pointer when executing bindings

src/bindings.c

@@ -126,9 +126,9 @@ static bool binding_in_current_group(const Binding *bind) {
 
 static void grab_keycode_for_binding(xcb_connection_t *conn, Binding *bind, uint32_t keycode) {
     /* Grab the key in all combinations */
-#define GRAB_KEY(modifier)                                                                       \
-    do {                                                                                         \
-        xcb_grab_key(conn, 0, root, modifier, keycode, XCB_GRAB_MODE_SYNC, XCB_GRAB_MODE_ASYNC); \
+#define GRAB_KEY(modifier)                                                                        \
+    do {                                                                                          \
+        xcb_grab_key(conn, 0, root, modifier, keycode, XCB_GRAB_MODE_ASYNC, XCB_GRAB_MODE_ASYNC); \
     } while (0)
     const int mods = (bind->event_state_mask & 0xFFFF);
     DLOG("Binding %p Grabbing keycode %d with event state mask 0x%x (mods 0x%x)\n",
@@ -166,7 +166,7 @@ void grab_all_keys(xcb_connection_t *conn) {
             const int keycode = binding_keycode->keycode;
             const int mods = (binding_keycode->modifiers & 0xFFFF);
             DLOG("Binding %p Grabbing keycode %d with mods %d\n", bind, keycode, mods);
-            xcb_grab_key(conn, 0, root, mods, keycode, XCB_GRAB_MODE_SYNC, XCB_GRAB_MODE_ASYNC);
+            xcb_grab_key(conn, 0, root, mods, keycode, XCB_GRAB_MODE_ASYNC, XCB_GRAB_MODE_ASYNC);
         }
     }
 }