Add Meta+x shortcut for CUT

Add a scrcpy shortcut to send the CUT keycode.

app/scrcpy.1

@@ -279,6 +279,10 @@ Collapse notification panel
 .B Meta+c
 Press COPY (Android >= 7), then copy device clipboard to computer
 
+.TP
+.B Meta+x
+Press CUT (Android >= 7)
+
 .TP
 .B Meta+v
 Paste computer clipboard to device

app/src/cli.c

@@ -248,6 +248,9 @@ scrcpy_print_usage(const char *arg0) {
         "        Press COPY (Android >= 7), then copy device clipboard to\n"
         "        computer\n"
         "\n"
+        "    " MOD "+x\n"
+        "        Press CUT (Android >= 7)\n"
+        "\n"
         "    " MOD "+v\n"
         "        Paste computer clipboard to device\n"
         "\n"

app/src/input_manager.c

@@ -70,6 +70,11 @@ action_menu(struct controller *controller, int actions) {
     send_keycode(controller, AKEYCODE_MENU, actions, "MENU");
 }
 
+static inline void
+action_cut(struct controller *controller, int actions) {
+    send_keycode(controller, AKEYCODE_CUT, actions, "CUT");
+}
+
 // turn the screen on if it was off, press BACK otherwise
 static void
 press_back_or_turn_screen_on(struct controller *controller) {
@@ -346,6 +351,14 @@ input_manager_process_key(struct input_manager *im,
                     request_device_clipboard(controller, true);
                 }
                 return;
+            case SDLK_x:
+                if (control && !shift && !repeat && down) {
+                    // For convenience (especially on macOS), bind Meta+x to
+                    // CUT (even if it is already accessible by pressing Ctrl+x
+                    // on the device)
+                    action_cut(controller, action);
+                }
+                return;
             case SDLK_v:
                 if (control && !repeat && down) {
                     if (shift) {