syscall.c: ensure that NT_PRSTATUS is defined

* syscall.c: Do not include <elf.h>.
(NT_PRSTATUS): New macro.

syscall.c

@@ -36,10 +36,6 @@
 
 /* for struct iovec */
 #include <sys/uio.h>
-/* for NT_PRSTATUS */
-#ifdef HAVE_ELF_H
-# include <elf.h>
-#endif
 
 #include "ptrace.h"
 
@@ -58,6 +54,10 @@
 # include <asm/psr.h>
 #endif
 
+#ifndef NT_PRSTATUS
+# define NT_PRSTATUS 1
+#endif
+
 #ifndef NSIG
 # warning: NSIG is not defined, using 32
 # define NSIG 32