* einfo.ads: Block_Node points to the identifier of the block, not to
	the block node itself, to preserve the link when the block is
	rewritten, e.g. within an if-statement with a static condition.

	* inline.adb (Cleanup_Scopes): recover block statement from block
	entity using new meaning of Block_Node.

	* sem_ch5.adb (Analyze_Block_Statement): set Block_Node to point to
	identifier of block node, rather than to node itself.

From-SVN: r47649