ada: Adjust locations in aspects on generic formal subprograms

ada: Adjust locations in aspects on generic formal subprograms

When instantiating a generic that has formal subprogram parameter with
contracts, e.g.:

  generic
    with procedure P with Pre => ..., Post => ...;
  ...

we create a wrapper that executes Pre/Post contracts before/after
calling the actual subprogram. Errors emitted for these contracts
will now have locations of the instance and not just of the generic.

gcc/ada/

	* sem_ch12.adb (Build_Subprogram_Wrappers): Adjust slocs of the
	copied aspects, just like we do in Build_Class_Wide_Expression for
	inherited class-wide contracts.