Use 'struct varobj_item' to represent name and value pair

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.