Fix internal error on function call returning extension of limited interface

Fix internal error on function call returning extension of limited interface

The problem occurs when this function call is the expression of a return in
a function returning the limited interface; in this peculiar case, there is
a mismatch between the callee, which has BIP formals but is not a BIP call,
and the caller, which is a BIP function, that is spotted by an assertion.

This is fixed by restoring the semantics of Is_Build_In_Place_Function_Call,
which returns again true only for calls to BIP functions, introducing the
Is_Function_Call_With_BIP_Formals predicate, which also returns true for
calls to functions with BIP formals that are not BIP functions, and moving
down the assertion in Expand_Simple_Function_Return.

gcc/ada/
	PR ada/112781
	* exp_ch6.ads (Is_Build_In_Place_Function): Adjust description.
	* exp_ch6.adb (Is_True_Build_In_Place_Function_Call): Delete.
	(Is_Function_Call_With_BIP_Formals): New predicate.
	(Is_Build_In_Place_Function_Call): Restore original semantics.
	(Expand_Call_Helper): Adjust conditions guarding the calls to
	Add_Dummy_Build_In_Place_Actuals to above renaming.
	(Expand_N_Extended_Return_Statement): Adjust to above renaming.
	(Expand_Simple_Function_Return): Likewise.  Move the assertion
	to after the transformation into an extended return statement.
	(Make_Build_In_Place_Call_In_Allocator): Remove unreachable code.
	(Make_Build_In_Place_Call_In_Assignment): Likewise.

gcc/testsuite/
	* gnat.dg/bip_prim_func2.adb: New test.
	* gnat.dg/bip_prim_func2_pkg.ads, gnat.dg/bip_prim_func2_pkg.adb:
	New helper package.