lib: use stdatomic.h for memory barriers

C11 gives us APIs for fencing logic.  Use that instead of a
a long, per-architecture, hand curated list of definitions.

lib/util/binfile.c

@@ -37,7 +37,6 @@
 
 #include "binfile.h"
 #include "elfparser.h"
-#include "util.h"
 
 struct bin_file_t
 {

lib/util/util.h

@@ -1,44 +0,0 @@
-#ifndef SP_UTIL_H
-#define SP_UTIL_H
-
-#ifdef __i386__
-#define read_barrier()           asm volatile("lock; addl $0,0(%%esp)" ::: "memory")
-#endif
-
-#ifdef __x86_64__
-#define read_barrier()           asm volatile("lfence" ::: "memory")
-#endif
-
-#ifdef __powerpc__
-#define read_barrier()           asm volatile ("sync" ::: "memory")
-#endif
-
-#ifdef __s390__
-#define read_barrier()           asm volatile("bcr 15,0" ::: "memory")
-#endif
-
-#ifdef __sh__
-#if defined(__SH4A__) || defined(__SH5__)
-# define read_barrier()          asm volatile("synco" ::: "memory")
-#else
-# define read_barrier()          asm volatile("" ::: "memory")
-#endif
-#endif
-
-#ifdef __hppa__
-#define read_barrier()           asm volatile("" ::: "memory")
-#endif
-
-#ifdef __arm__
-#define read_barrier()           asm volatile("dsb" ::: "memory")
-#endif
-
-/*
- * Fallback to a full memory barrier if the architecture is not yet
- * supported with a lighter read barrier.
- */
-#ifndef read_barrier
-#define read_barrier()           __sync_synchronize()
-#endif
-
-#endif /* SP_UTIL_H */