ptrace: generic PTRACE_SINGLEBLOCK

This makes ptrace_request handle PTRACE_SINGLEBLOCK along with
PTRACE_CONT et al.  The new generic code makes use of the
arch_has_block_step macro and generic entry points on machines
that define them.

[ mingo@elte.hu: bugfix ]

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 1febc54..515bff0 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -187,7 +187,7 @@
  * supports step-until-branch for user mode.  It can be a constant or it
  * can test a CPU feature bit.
  */
-#define arch_has_single_step()		(0)
+#define arch_has_block_step()		(0)
 
 /**
  * user_enable_block_step - step until branch in user-mode task