Fortran: Use OpenACC's acc_on_device builtin, fix OpenMP' __builtin_is_initial_device

Fortran: Use OpenACC's acc_on_device builtin, fix OpenMP' __builtin_is_initial_device

It turned out that 'if (omp_is_initial_device() .eqv. true)' gave an ICE
due to comparing 'int' with 'logical(4)'. When digging deeper, it also
turned out that when the procedure pointer is needed, the builtin cannot
be used, either.  (Follow up to r15-2799-gf1bfba3a9b3f31 )

Extend the code to also use the builtin acc_on_device with OpenACC,
which was previously only used in C/C++.  Additionally, fix folding
when offloading is not enabled.

Fixes additionally the BT_BOOL data type, which was 'char'/integer(1)
instead of bool, backing the booleaness; use bool_type_node as the rest
of GCC.

gcc/fortran/ChangeLog:

	* gfortran.h (gfc_option_t): Add disable_acc_on_device.
	* options.cc (gfc_handle_option): Handle -fno-builtin-acc_on_device.
	* trans-decl.cc (gfc_get_extern_function_decl): Move
	__builtin_omp_is_initial_device handling to ...
	* trans-expr.cc (get_builtin_fn): ... this new function.
	(conv_function_val): Call it.
	(update_builtin_function): New.
	(gfc_conv_procedure_call): Call it.
	* types.def (BT_BOOL): Fix type by using bool_type_node.

gcc/ChangeLog:

	* gimple-fold.cc (gimple_fold_builtin_acc_on_device): Also fold
	when offloading is not configured.

libgomp/ChangeLog:

	* libgomp.texi (TR13): Fix minor typos.
	(omp_is_initial_device): Improve wording.
	(acc_on_device): Note how to disable the builtin.
	* testsuite/libgomp.oacc-fortran/acc_on_device-1-1.f90: Remove TODO.
	* testsuite/libgomp.oacc-fortran/acc_on_device-1-2.f: Likewise.
	Add -fno-builtin-acc_on_device.
	* testsuite/libgomp.oacc-fortran/acc_on_device-1-3.f: Likewise.
	* testsuite/libgomp.oacc-c-c++-common/routine-nohost-1.c: Update
	dg- as !offloading_enabled now compile-time expands acc_on_device.
	* testsuite/libgomp.fortran/target-is-initial-device-3.f90: New test.
	* testsuite/libgomp.oacc-fortran/acc_on_device-2.f90: New test.