coredump: update coredump-related headers

Create a new header file, fs/coredump.h, which contains functions only
used by the new coredump.c.  It also moves do_coredump to the
include/linux/coredump.h header file, for consistency.

Signed-off-by: Alex Kelly <alex.page.kelly@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/signal.c b/kernel/signal.c
index 2c681f1..2ad3f59 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -17,6 +17,7 @@
 #include <linux/fs.h>
 #include <linux/tty.h>
 #include <linux/binfmts.h>
+#include <linux/coredump.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/ptrace.h>