strtok_r: Include features.h and reinstate "restrict".

src/system/kernel/lib/Jamfile

@@ -54,6 +54,7 @@ local muslSources =
 	ffsll.c
 	rand.c
 	rand_r.c
+	strtok_r.c
 	;
 
 SourceHdrs $(muslSources) :
@@ -148,7 +149,6 @@ KernelMergeObject kernel_lib_posix.o :
 	strspn.c
 	strstr.c
 	strtok.c
-	strtok_r.c
 	strupr.c
 
 	$(muslSources)

src/system/libroot/posix/musl/string/strtok_r.c

@@ -1,6 +1,7 @@
 #include <string.h>
+#include "features.h"
 
-char *strtok_r(char *s, const char *sep, char **p)
+char *strtok_r(char *restrict s, const char *restrict sep, char **restrict p)
 {
 	if (!s && !(s = *p)) return NULL;
 	s += strspn(s, sep);