Implement add_key, keyctl, and request_key decoding

* keyctl.c: New file.
* linux/keyctl.h: Likewise.
* Makefile.am (strace_SOURCES): Add keyctl.c.
(EXTRA_DIST): Add linux/keyctl.h.
* linux/dummy.h (sys_add_key, sys_keyctl, sys_request_key): Remove.
* linux/syscall.h (sys_add_key, sys_keyctl, sys_request_key): New
prototypes.
diff --git a/Makefile.am b/Makefile.am
index 65929dc..a9d2ff0 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -28,6 +28,7 @@
 	ioprio.c	\
 	ipc.c		\
 	kexec.c		\
+	keyctl.c	\
 	loop.c		\
 	mem.c		\
 	mtd.c		\
@@ -115,6 +116,7 @@
 	linux/ioctlent.sh		\
 	linux/ioctlsort.c		\
 	linux/kexec.h			\
+	linux/keyctl.h			\
 	linux/m68k/ioctlent.h.in	\
 	linux/m68k/syscallent.h		\
 	linux/metag/ioctlent.h.in	\