Use 'struct varobj_item' to represent name and value pair

Hi,
name and value pair is widely used in varobj.c.  This patch is to add
a new struct varobj_item to represent them, so that the number of
function arguments can be reduced.  Finally, the iteration is done on
'struct varobj_item' instead of PyObject after this patch series.

 V2:
 - Fix changelog entry.
 - Fix one grammatical mistake.

gdb:

2014-06-12  Yao Qi  <yao@codesourcery.com>

	* varobj.c (struct varobj_item): New structure.
	(create_child_with_value): Update declaration.
	(varobj_add_child): Replace arguments 'name' and 'value' with
	'item'.  All callers updated.
	(install_dynamic_child): Likewise.
	(update_dynamic_varobj_children): Likewise.
	(varobj_add_child): Likewise.
	(create_child_with_value): Likewise.
Generalize varobj iterator

This patch generalizes varobj iterator, in a python-independent way.
Note varobj_item is still a typedef of PyObject, we can only focus on
API changes, and leave the data type changes to the next patch.  As a
result, we include "varobj-iter.h" after the typedef of PyObject in
varobj.c, but it is an intermediate state.  Finally, varobj-iter.h is
independent of PyObject.

This change is helpful to move some python-related code out of
varobj.c.

 V2:
  - Fix a missing cleanup.
  - Fix typos.
  - Use XNEW.
  - Check against NULL explicitly.
  - Update copyright year for new added files.

 V3:
  - Call PyGILState_Ensure before Py_XDECREF.
  - Use CPYCHECKER_STEALS_REFERENCE_TO_ARG.
  - Code indentation.

 V4:
  - use varobj_ensure_python_env instead of PyGILState_Ensure.

gdb:

2014-06-12  Pedro Alves  <pedro@codesourcery.com>
	    Yao Qi  <yao@codesourcery.com>

	* Makefile.in (SUBDIR_PYTHON_OBS): Add "py-varobj.o".
	(SUBDIR_PYTHON_SRCS): Add "python/py-varobj.c".
	(HFILES_NO_SRCDIR): Add "varobj-iter.h".
	(py-varobj.o): New rule.
	* python/py-varobj.c: New file.
	* python/python-internal.h (py_varobj_get_iterator): Declare.
	* varobj-iter.h: New file.
	* varobj.c: Include "varobj-iter.h"
	(struct varobj) <child_iter>: Change its type from "PyObject *"
	to "struct varobj_iter *".
	<saved_item>: Likewise.
	[HAVE_PYTHON] (varobj_ensure_python_env): Make it extern.
	[HAVE_PYTHON] (varobj_get_iterator): New function.
	(update_dynamic_varobj_children) [HAVE_PYTHON]: Move
	python-specific code to python/py-varobj.c.
	(install_visualizer): Call varobj_iter_delete instead of
	Py_XDECREF.
	* varobj.h (varobj_ensure_python_env): Declare.
Iterate over 'struct varobj_item' instead of PyObject

In previous patch, "saved_item" is still a PyOjbect and iteration is
still performed over PyObject.  This patch continues to decouple
iteration from python code, so it changes its type to "struct
varobj_item *", so that the iterator itself is independent of python.

 V2:
 - Call varobj_delete_iter in free_variable.
 - Fix changelog entries.
 - Use XNEW.

 V3:
 - Return NULL early in py_varobj_iter_next if gdb_python_initialized
   is false.

gdb:

2014-06-12  Pedro Alves  <pedro@codesourcery.com>
	    Yao Qi  <yao@codesourcery.com>

	* python/py-varobj.c (py_varobj_iter_next): Return NULL if
	gdb_python_initialized is false.  Move some code from varobj.c.
	* varobj-iter.h (struct varobj_item): Moved from varobj.c.
	* varobj.c: Move "varobj-iter.h" inclusion earlier.
	(struct varobj_item): Moved to varobj-iter.h".
	(varobj_clear_saved_item): New function.
	(update_dynamic_varobj_children): Move python-related code to
	py-varobj.c.
	(free_variable): Call varobj_clear_saved_item and
	varobj_iter_delete.
Remove #if HAVE_PYTHON

This patch removes some unnecessary "#if HAVE_PYTHON" so that more
code is generalized.

gdb:

2014-06-12  Pedro Alves  <pedro@codesourcery.com>
	    Yao Qi  <yao@codesourcery.com>

	* varobj.c: Remove "#if HAVE_PYTHON" and "#endif".
	(varobj_get_iterator): Wrap up code for pretty-printer by
	"#if HAVE_PYTHON" and "#endif".
	(update_dynamic_varobj_children): Likewise.
Rename varobj_pretty_printed_p to varobj_is_dynamic_p

We think varobj with --available-children-only behaves like a dynamic
varobj, so dyanmic varobj is not pretty-printer specific.  We rename
varobj_pretty_printed_p to varobj_is_dynamic_p, so that we can handle
available-children-only checking in varobj_is_dynamic_p in the next
patch.

gdb:

2014-06-12  Yao Qi  <yao@codesourcery.com>

	* varobj.c (varobj_pretty_printed_p): Rename to ...
	(varobj_is_dynamic_p): ... this.  New function.
	* varobj.h (varobj_pretty_printed_p): Remove declaration.
	(varobj_is_dynamic_p): Declare.
	* mi/mi-cmd-var.c (print_varobj): All callers updated.
	(mi_print_value_p, varobj_update_one): Likewise.
Use varobj_is_dynamic_p more widely

Use varobj_is_dynamic_p more widely so that the callers of
varobj_is_dynamic_p are unchanged when we add available-children-only
stuff in varobj_is_dynamic_p.

gdb:

2014-06-12  Yao Qi  <yao@codesourcery.com>

	* varobj.c (varobj_get_num_children): Call
	varobj_is_dynamic_p.
	(varobj_list_children): Likewise.
	(varobj_update): Likewise.  Update comments.