input: qapi: add pause key

It's missing.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

qapi-schema.json

@@ -3556,7 +3556,7 @@
 #
 # Since: 1.3.0
 #
-# 'unmapped' since 2.0
+# 'unmapped' and 'pause' since 2.0
 ##
 { 'enum': 'QKeyCode',
   'data': [ 'unmapped',
@@ -3574,7 +3574,7 @@
             'kp_9', 'less', 'f11', 'f12', 'print', 'home', 'pgup', 'pgdn', 'end',
             'left', 'up', 'down', 'right', 'insert', 'delete', 'stop', 'again',
             'props', 'undo', 'front', 'copy', 'open', 'paste', 'find', 'cut',
-             'lf', 'help', 'meta_l', 'meta_r', 'compose' ] }
+             'lf', 'help', 'meta_l', 'meta_r', 'compose', 'pause' ] }
 
 ##
 # @KeyValue