libdebugger: Fixes to debugging, ARM support, locking, and gcc-7.1 warnings.

- Add `printk` support to aid multi-core debugging.
- Add lock trace to aid lock debugging.
- Fixes to gcc-7.1 warnings.
- Fixes from ticket #2879.
- Add verbose command controls.
- Change using the RTEMS sys/lock.h API to manage exception threads.
- ARM hardware breakpoint fixes. Support for SMP stepping
  is not implemented, this requires use of the context id
  register.

Closes #2879.

cpukit/libdebugger/rtems-debugger-target.h

@@ -1,5 +1,6 @@
 /*
- * Copyright (c) 2016 Chris Johns <chrisj@rtems.org>.  All rights reserved.
+ * Copyright (c) 2016-2017 Chris Johns <chrisj@rtems.org>.
+ * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -193,6 +194,16 @@ extern int rtems_debugger_target_swbreak_insert(void);
  */
 extern int rtems_debugger_target_swbreak_remove(void);
 
+/**
+ * Insert hardware breakpoints into the hardware.
+ */
+extern int rtems_debugger_target_hwbreak_insert(void);
+
+/**
+ * Remove hardware breakpoints from the hardware.
+ */
+extern int rtems_debugger_target_hwbreak_remove(void);
+
 /**
  * Hardware breakpoints.
  */
@@ -208,9 +219,14 @@ extern rtems_debugger_target_exc_action
 rtems_debugger_target_exception(CPU_Exception_frame* frame);
 
 /**
- * Set the thread's exception stack frame pointer.
+ * See if the thread is an exception thread.
  */
-extern int rtems_debugger_target_set_exception_frame(rtems_debugger_thread* thread);
+extern void rtems_debugger_target_exception_thread(rtems_debugger_thread* thread);
+
+/**
+ * If the thread is an exception thread, resume it.
+ */
+extern void rtems_debugger_target_exception_thread_resume(rtems_debugger_thread* thread);
 
 /**
  * Target instruction cache sync. This depends on the target but it normally