various: sort some standard headers

since i was going to fix the include order of stdatomic, might as well
sort the surrouding includes in accordance with the project's coding
style.

some headers can sometime require specific include order. standard
library headers usually don't. but mpv might "hack into" the standard
headers (e.g pthreads) so that complicates things a bit more.

hopefully nothing breaks. if it does, the style guide is to blame.

options/m_config_core.c

@@ -15,14 +15,15 @@
  * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <stdlib.h>
-#include <stdio.h>
+#include <assert.h>
 #include <errno.h>
+#include <pthread.h>
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <strings.h>
-#include <assert.h>
-#include <stdbool.h>
-#include <pthread.h>
 
 #include "m_config_core.h"
 #include "options/m_option.h"
@@ -31,7 +32,6 @@
 #include "common/msg.h"
 #include "common/msg_control.h"
 #include "misc/dispatch.h"
-#include <stdatomic.h>
 
 // For use with m_config_cache.
 struct m_config_shadow {

options/m_config_frontend.c

@@ -15,15 +15,16 @@
  * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <float.h>
-#include <stdlib.h>
-#include <stdio.h>
+#include <assert.h>
 #include <errno.h>
+#include <float.h>
+#include <pthread.h>
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <strings.h>
-#include <assert.h>
-#include <stdbool.h>
-#include <pthread.h>
 
 #include "libmpv/client.h"
 
@@ -36,7 +37,6 @@
 #include "common/msg_control.h"
 #include "misc/dispatch.h"
 #include "misc/node.h"
-#include <stdatomic.h>
 
 extern const char mp_help_text[];
 

options/m_config_frontend.h

@@ -17,9 +17,10 @@
 
 #pragma once
 
+#include <stdatomic.h>
+#include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
-#include <stdbool.h>
 
 #include "common/common.h"
 #include "common/global.h"
@@ -29,7 +30,6 @@
 #include "misc/bstr.h"
 #include "misc/dispatch.h"
 #include "options/m_option.h"
-#include <stdatomic.h>
 
 // m_config provides an API to manipulate the config variables in MPlayer.
 // It makes use of the Options API to provide a context stack that