[Ada] Do not query the representation information in CodePeer/GNATprove

[Ada] Do not query the representation information in CodePeer/GNATprove

Representation information generated when user calls the compiler with -gnatR
switch is not available when running the frontend inside CodePeer or GNATprove.
Do not query such information in that case, as this leads to spurious messages
that it is not available.

There is no impact on compilation.

2018-06-11  Yannick Moy  <moy@adacore.com>

gcc/ada/

	* gnat1drv.adb: Do not check representation information in CodePeer and
	GNATprove modes, as these modes call a special backend instead of gigi,
	so do not have the information.

From-SVN: r261414