Add unique syscall entry numbers (SENs)

* Makefile.am (BUILT_SOURCES, CLEANFILES): Add sen.h.
(syscallent_names, syscallent_patterns, syscallent_files): New variables.
(sen.h): New rule.
* defs.h (struct sysent): Add sen field.
* generate_sen.sh: New file.
* linux/syscall.h: Include "sen.h".
* syscall.c (SEN_NAME): New temporary macro.
(SEN): Use it to prepend syscall entry number.
diff --git a/defs.h b/defs.h
index ede39b4..25e377a 100644
--- a/defs.h
+++ b/defs.h
@@ -249,6 +249,7 @@
 typedef struct sysent {
 	unsigned nargs;
 	int	sys_flags;
+	int	sen;
 	int	(*sys_func)();
 	const char *sys_name;
 } struct_sysent;