[Ada] Crash due to missing freeze nodes in transient scope

[Ada] Crash due to missing freeze nodes in transient scope

The following patch updates the freezing of expressions to insert the
generated freeze nodes prior to the expression that produced them when
the context is a transient scope within a type initialization procedure.
This ensures that the nodes are properly interleaved with respect to the
constructs that generated them.

2019-07-01  Hristian Kirtchev  <kirtchev@adacore.com>

gcc/ada/

	* freeze.adb (Freeze_Expression): Remove the horrible useless
	name hiding of N. Insert the freeze nodes generated by the
	expression prior to the expression when the nearest enclosing
	scope is transient.

gcc/testsuite/

	* gnat.dg/freezing1.adb, gnat.dg/freezing1.ads,
	gnat.dg/freezing1_pack.adb, gnat.dg/freezing1_pack.ads: New
	testcase.

From-SVN: r272854