include: remove needless c99_compat.h includes

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16812>

include/c11/threads.h

@@ -35,8 +35,6 @@
 #define TIME_UTC 1
 #endif
 
-#include "c99_compat.h" /* for `inline` */
-
 /*---------------------------- types ----------------------------*/
 typedef void (*tss_dtor_t)(void*);
 typedef int (*thrd_start_t)(void*);

include/c99_math.h

@@ -35,7 +35,6 @@
 #define _C99_MATH_H_
 
 #include <math.h>
-#include "c99_compat.h"
 
 
 /* This is to ensure that we get M_PI, etc. definitions */