[Ada] Unnesting: properly handle local subprogram in declare blocks

[Ada] Unnesting: properly handle local subprogram in declare blocks

2018-05-30  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_ch7.adb (Check_Unnesting_Elaboration_Code): The statement part of
	a package body that is a compilation unit may contain blocks that
	declare local subprograms.  In Subprogram_Unnesting Mode such
	subprograms must be handled as nested inside the (implicit) elaboration
	procedure that executes that statement part. To handle properly uplevel
	references we construct that subprogram explicitly, to contain blocks
	and inner subprograms, The statement part of the compilation unit
	becomes a call to this subprogram. This is only done if blocks are
	present in the statement list of the body.

From-SVN: r260927