ada: Attach pre/post on access-to-subprogram to internal subprogram type

ada: Attach pre/post on access-to-subprogram to internal subprogram type

Aspects Pre/Post that annotate access-to-subprogram type were attached
to the source entity (whose kind is either E_Access_Subprogram_Type or
E_Access_Protected_Subprogram_Type). However, it is more convenient to
attach them to the internal entity (whose kind is E_Subprogram_Type), so
that both Pre/Post aspects and First_Formal/Next_Formal chain are
attached to the same entity, just like for ordinary subprograms.

The drawback of having the Post aspect attached to an internal entity is
that name in prefixes of attribute Result no longer match the name of
entity where this Post aspect is attached. However, currently there is
no code that relies on this matching and, in general, there are fewer
routines that deal with attribute Result so they are easier to adapt
than the code that queries the Pre/Post aspects.

gcc/ada/

	* contracts.adb
	(Add_Pre_Post_Condition): Attach pre/post aspects to E_Subprogram_Type
	entity.
	(Analyze_Entry_Or_Subprogram_Contract): Adapt to use full type
	declaration for a contract attached to E_Subprogram_Type entity.
	* sem_prag.adb
	(Analyze_Pre_Post_Condition): Add pre/post aspects to the designed type.