[Ada] Removing support for SCIL "contract-only" subprogram bodies

[Ada] Removing support for SCIL "contract-only" subprogram bodies

Remove support added for CodePeer (which was never enabled by default;
it was controlled by the -gnatd.K option) for generation of SCIL
"contract-only" subprogram bodies. These were intended for use when a
subprogram's "real" body is unavailable but the subprogram spec has
pre/post-conditions specified.

2019-07-05  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* debug.adb (-gnatd.K): Leave available this switch.
	* contracts.adb (Build_And_Analyze_Contract_Only_Subprograms):
	Remove.
	* scil_ll.ads, scil_ll.adb (Contract_Only_Body_Flag,
	Contract_Only_Body_Nodes, Get_Contract_Only_Body,
	Is_Contract_Only_Body, Set_Contract_Only_Body): Remove.

From-SVN: r273111