[Ada] Use renamings in GNATprove mode for side-effects extraction

[Ada] Use renamings in GNATprove mode for side-effects extraction

In the GNATprove mode for formal verification, prefer renamings over
declaration of a constant to extract side-effects from expressions,
whenever the constant could be of an owning type, as declaring a
constant of an owning type has an effect on ownership which is
undesirable.

There is no impact on compilation.

2019-07-10  Yannick Moy  <moy@adacore.com>

gcc/ada/

	* exp_util.adb (Remove_Side_Effects): Prefer renamings for
	objects of possible owning type in GNATprove mode.

From-SVN: r273324