[Ada] Support access types in GNATprove

[Ada] Support access types in GNATprove

SPARK RM has been updated to support access types in SPARK. Part of this
support is that now SPARK RM 3.1 lists access types as having full
default initialization. Now updated.

There is no impact on compilation.

2018-12-11  Yannick Moy  <moy@adacore.com>

gcc/ada/

	* sem_util.adb (Has_Full_Default_Initialization): Consider
	access types as having full default initialization.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@266990 138bc75d-0d04-0410-961f-82ee72b054a4