[PATCH 6/7] OpenMP 4.0 offloading infrastructure: option handling.

gcc/
	* common.opt (foffload, foffload-abi): New options.
	* config/i386/i386.c (ix86_offload_options): New static function.
	(TARGET_OFFLOAD_OPTIONS): Define.
	* coretypes.h (enum offload_abi): New enum.
	* doc/tm.texi: Regenerate.
	* doc/tm.texi.in (TARGET_OFFLOAD_OPTIONS): Document.
	* gcc.c (offload_targets): New static variable.
	(handle_foffload_option): New static function.
	(driver_handle_option): Handle OPT_foffload_.
	(driver::maybe_putenv_OFFLOAD_TARGETS): Set OFFLOAD_TARGET_NAMES
	according to offload_targets.
	* hooks.c (hook_charptr_void_null): New hook.
	* hooks.h (hook_charptr_void_null): Declare.
	* lto-opts.c: Include lto-section-names.h.
	(lto_write_options): Append options from target offload_options hook and
	store them to offload_lto section.  Do not store target-specific,
	driver and diagnostic options in offload_lto section.
	* lto-wrapper.c (merge_and_complain): Handle OPT_foffload_ and
	OPT_foffload_abi_.
	(append_compiler_options, append_linker_options)
	(append_offload_options): New static functions.
	(compile_offload_image): Add new arguments with options.
	Call append_compiler_options and append_offload_options.
	(compile_images_for_offload_targets): Add new arguments with options.
	(find_and_merge_options): New static function.
	(run_gcc): Outline options handling into the new functions:
	find_and_merge_options, append_compiler_options, append_linker_options.
	* opts.c (common_handle_option): Don't handle OPT_foffload_.
	Forbid OPT_foffload_abi_ for non-offload compiler.
	* target.def (offload_options): New target hook.

Co-Authored-By: Andrey Turetskiy <andrey.turetskiy@intel.com>
Co-Authored-By: Ilya Verbin <ilya.verbin@intel.com>

From-SVN: r217493