Fix playlist API header includes

Most playlist headers did not compile in pure C, as types like bool and size_t are used in calls. Added the proper includes as needed to make each header compile if included standalone.

src/playlist/api/projectM-4/playlist_callbacks.h

@@ -27,7 +27,8 @@
 #pragma once
 
 #include "projectM-4/playlist_types.h"
-#include <stdint.h>
+
+#include <stdbool.h>
 
 #ifdef __cplusplus
 extern "C" {

src/playlist/api/projectM-4/playlist_filter.h

@@ -28,6 +28,8 @@
 
 #include "projectM-4/playlist_types.h"
 
+#include <stddef.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif

src/playlist/api/projectM-4/playlist_items.h

@@ -28,6 +28,9 @@
 
 #include "projectM-4/playlist_types.h"
 
+#include <stdint.h>
+#include <stdbool.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif

src/playlist/api/projectM-4/playlist_playback.h

@@ -28,6 +28,9 @@
 
 #include "projectM-4/playlist_types.h"
 
+#include <stdint.h>
+#include <stdbool.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif