tools/lib/lockdep: Add missing declaration of 'pr_cont()'

Commit:

  681fbec8 ("lockdep: Use consistent printing primitives")

has moved lockdep away from using printk() for printing.

The commit added usage of pr_cont() which wasn't wrapped in the
userspace headers, causing the following warning for the
liblockdep build:

	../../../kernel/locking/lockdep.c:3544:2: warning: implicit declaration of function 'pr_cont' [-Wimplicit-function-declaration]

Adding an empty declaration of 'pr_cont' fixes the problem.
Signed-off-by: Mengting Zhang <zhangmengting@huawei.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: a.p.zijlstra@chello.nl
Link: http://lkml.kernel.org/r/20171212181644.11913-2-alexander.levin@verizon.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

tools/include/linux/lockdep.h

@@ -48,6 +48,7 @@ static inline int debug_locks_off(void)
 #define printk(...) dprintf(STDOUT_FILENO, __VA_ARGS__)
 #define pr_err(format, ...) fprintf (stderr, format, ## __VA_ARGS__)
 #define pr_warn pr_err
+#define pr_cont pr_err
 
 #define list_del_rcu list_del