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.
4 files changed