[Ada] Update for Ownership rules for access types according to AI12-0240

[Ada] Update for Ownership rules for access types according to AI12-0240

The implementation of these Ownership rules for safe pointers and
automatic memory management is still a prototype at an experimental
stage.

To activate the checks, the code should be compiled with the debug flag
-gnatdF and the flag -gnatd.F for setting the context for formal
verification of SPARK.

These changes do not affect compilation.

2018-08-21  Maroua Maalej  <maalej@adacore.com>

gcc/ada/

	* sem_spark.adb (Check_Call_Statement): Check global and formal
	parameter permissions at call sites.
	(Check_Callable_Body): Assume permissions on globals and
	parameters depending on their modes then analyse the body
	operations.
	(Check_Declaration): Consider both deep (including elementary
	access) object declarations and normal variables. First check
	whether the deep object is of Ownership Aspec True or not, then,
	depending on its initialization, assign the appropriate state.
	Check related to non access type variables deal with
	initialization value permissions.
	(Check_Expression): Check nodes used in the expression being
	analyzed.
	(Check_Globals): Call by Check_Call_Statement to perform the
	check on globals.
	(Check_List): Call Check_Node on each element of the list.
	(Check_Loop_Statement): Check the Iteration_Scheme and loop
	statements.
	(Check_Node): Main traversal procedure to check safe pointer usage.
	(Check_Package_Body): Check subprogram's body.
	(Check_Param_In): Take a formal and an actual parameter and
	Check the permission of every in-mode parameter.
	(Check_Param_Out): Take a formal and an actual parameter and
	check the state of out-mode and in out-mode parameters.
	(Check_Statement): Check statements other than procedure call.
	(Get_Perm, Get_Perm_Or_Tree, Get_Perm_Tree): Find out the state
	related to the given name.
	(Is_Deep): Return True if an object is of access type or has
	subfields of access type.
	(Perm_Error, Perm_Error_Subprogram_End): Add an error message
	whenever the found state on the given name is different from the
	one expected (in the statement being analyzed).
	(Process_Path): Given an operation and a current state, call
	Perm_Error if there is any mismatch.
	(Return_Declarations, Return_Globals, Return_The_Global): Check
	the state of a given name at the end of the subprogram. These
	procedures may change depending on how we shall finally deal
	with globals and the rhs state in a move operation.
	(Set_Perm_Extensions, Set_Perm_Prefixes_Borrow,
	Set_Perm_Prefixes, Setup_Globals, Setup_Parameter_Or_Global,
	Setup_Parameters): Set up the new states to the given node and
	up and down the tree after an operation.
	(Has_Ownership_Aspect_True): This function may disappear later
	when the Ownership Aspect will be implemented in the FE.

From-SVN: r263727