Fix implicit mapping for array slices on lexically-enclosing data constructs (PR70828)

Fix implicit mapping for array slices on lexically-enclosing data constructs (PR70828)

2018-08-28  Julian Brown  <julian@codesourcery.com>
	    Cesar Philippidis  <cesar@codesourcery.com>

	gcc/
	* gimplify.cc (oacc_array_mapping_info): New struct.
	(gimplify_omp_ctx): Add decl_data_clause hash map.
	(new_omp_context): Zero-initialise above.
	(delete_omp_context): Delete above if allocated.
	(gimplify_scan_omp_clauses): Scan for array mappings on data constructs,
	and record in above map.
	(gomp_oacc_needs_data_present): New function.
	(gimplify_adjust_omp_clauses_1): Handle data mappings (e.g. array
	slices) declared in lexically-enclosing data constructs.
	* omp-low.cc (lower_omp_target): Allow decl for bias not to be present
	in OpenACC context.

	gcc/testsuite/
	* c-c++-common/goacc/acc-data-chain.c: New test.
	* gfortran.dg/goacc/pr70828.f90: New test.

	libgomp/
	* testsuite/libgomp.oacc-c-c++-common/pr70828.c: New test.
	* testsuite/libgomp.oacc-fortran/implicit_copy.f90: New test.
	* testsuite/libgomp.oacc-fortran/pr70828.f90: New test.
	* testsuite/libgomp.oacc-fortran/pr70828-2.f90: New test.
	* testsuite/libgomp.oacc-fortran/pr70828-3.f90: New test.
	* testsuite/libgomp.oacc-fortran/pr70828-4.f90: New test.
	* testsuite/libgomp.oacc-fortran/pr70828-5.f90: New test.
	* testsuite/libgomp.oacc-fortran/pr70828-6.f90: New test.