Consistently generate debug info for elaboration variables

Consistently generate debug info for elaboration variables

This makes sure that debug info is generated for elaboration variables,
even if the variables are not generated exclusively for this purpose.

gcc/ada/
	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Named_Integer>: Do
	not pass default value in call to create_var_decl.
	<E_Variable>: Likewise.
	<E_Record_Subtype>: Both pass true for const_flag and false for
	const_decl_allowed_p in call to create_var_decl.
	Small tweaks in the generic record type case.
	(elaborate_expression): Rename need_debug into need_for_debug and
	adjust throughout.
	(elaborate_expression_1): Likewise.  Pass Needs_Debug_Info instead
	of need_for_debug in call to create_var_decl.
	(elaborate_expression_2): Likewise.
	* gcc-interface/utils.c (maybe_pad_type): Pass false for
	const_decl_allowed_p in call to create_var_decl.