Create subobject value in pretty printer

Create subobject value in pretty printer

Nowadays, we create a value of subobject in pretty printer with 'address'
being used,

  value = value_from_contents_and_address (type, valaddr + embedded_offset,
					   address + embedded_offset);

  set_value_component_location (value, val);
  /* set_value_component_location resets the address, so we may
     need to set it again.  */
  if (VALUE_LVAL (value) != lval_internalvar
      && VALUE_LVAL (value) != lval_internalvar_component
      && VALUE_LVAL (value) != lval_computed)
    set_value_address (value, address + embedded_offset);

value_from_contents_and_address creates a value from memory, but the
value we are pretty-printing may not from memory at all.

Instead of using value_from_contents_and_address, we create a value
of subobject with the same location as object's but different offset.
We avoid using address in this way.  As a result, parameter 'address'
in apply_val_pretty_printer is no longer needed, we can remove it in
next step.

We've already had the location of the 'whole' value, so it is safe
to assume we can create a value of 'component' or 'suboject' value
at the same location but with different offset.

gdb:

2016-11-21  Yao Qi  <yao.qi@linaro.org>

	* guile/scm-pretty-print.c (gdbscm_apply_val_pretty_printer):
	Don't call value_from_contents_and_address and
	set_value_address.  Call value_from_component.
	* python/py-prettyprint.c (gdbpy_apply_val_pretty_printer):
	Likewise.
	* value.c (value_from_component): New function.
	* value.h (value_from_component): Likewise.
	* valarith.c (value_subscripted_rvalue): Call
	value_from_component.