We have two families of routines to query entity properties: Known_XXX
and Unknown_XXX. They now simply negate each other instead of negating
their complex conditions.

Code cleanup only related to handling of Alignment in GNATprove;
semantics is unaffected.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* einfo-utils.adb
	(Unknown_Alignment): Simply negate the Known_ counterpart.
	(Unknown_Component_Bit_Offset): Likewise.
	(Unknown_Esize): Likewise.
	(Unknown_Normalized_First_Bit): Likewise.
	(Unknown_Normalized_Position): Likewise.
	(Unknown_Normalized_Position_Max): Likewise.
	(Unknown_RM_Size): Likewise.