Enhance reboot decoding

* linux/reboot.h: New file.
* system.c (bootflags1, bootflags2, bootflags3, sys_reboot): Move...
* reboot.c: ... here.
(bootflags2, bootflags3): Update constants.
* Makefile.am (strace_SOURCES): Add reboot.c.
(EXTRA_DIST): Add linux/reboot.h.
diff --git a/Makefile.am b/Makefile.am
index 55cd4cc..5524293 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -34,6 +34,7 @@
 	process.c	\
 	ptp.c		\
 	quota.c		\
+	reboot.c	\
 	resource.c	\
 	scsi.c		\
 	signal.c	\
@@ -137,6 +138,7 @@
 	linux/powerpc/syscallent.h	\
 	linux/powerpc/syscallent1.h	\
 	linux/ptp_clock.h		\
+	linux/reboot.h			\
 	linux/s390/ioctlent.h.in	\
 	linux/s390/syscallent.h		\
 	linux/s390x/ioctlent.h.in	\