various: reduce the include scope of some public headers

input/input.c

@@ -28,6 +28,8 @@
 #include <fcntl.h>
 #include <assert.h>
 
+#include <libmpv/client.h>
+
 #include "osdep/io.h"
 #include "misc/rendezvous.h"
 

input/ipc.c

@@ -15,6 +15,8 @@
  * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <libmpv/client.h>
+
 #include "common/msg.h"
 #include "input/input.h"
 #include "misc/json.h"