lua: wrap mpv_get_wakeup_pipe()

Pretty much experimental for issue #661.

DOCS/man/en/lua.rst

@@ -334,6 +334,10 @@ The ``mp`` module is preloaded, although it can be loaded manually with
     long time, but doesn't really need access to the player (like a network
     operation). Note that you still can access the player at any time.
 
+``mp.get_wakeup_pipe()``
+    Calls ``mpv_get_wakeup_pipe()`` and returns the read end of the wakeup
+    pipe. (See ``client.h`` for details.)
+
 ``mp.enable_messages(level)``
     Set the minimum log level of which mpv message output to receive. These
     messages are normally printed to the terminal. By calling this function,

player/lua.c

@@ -1047,6 +1047,13 @@ static int script_format_time(lua_State *L)
     return 1;
 }
 
+static int script_get_wakeup_pipe(lua_State *L)
+{
+    struct script_ctx *ctx = get_ctx(L);
+    lua_pushinteger(L, mpv_get_wakeup_pipe(ctx->client));
+    return 1;
+}
+
 struct fn_entry {
     const char *name;
     int (*fn)(lua_State *L);
@@ -1085,6 +1092,7 @@ static struct fn_entry fn_list[] = {
     FN_ENTRY(input_set_section_mouse_area),
     FN_ENTRY(format_time),
     FN_ENTRY(enable_messages),
+    FN_ENTRY(get_wakeup_pipe),
 };
 
 // On stack: mp table