common.opt: Split up -fisolate-erroneous-paths into -fisolate-erroneous-paths-dereference...

	* common.opt: Split up -fisolate-erroneous-paths into
	-fisolate-erroneous-paths-dereference and
	-fisolate-erroneous-paths-attribute.
	* invoke.texi: Corresponding changes.
	* gimple.c (infer_nonnull_range):  Add and use new arguments
	to control what kind of statements can be used to infer a
	non-null range.
	* gimple.h (infer_nonnull_range): Update prototype.
	* tree-vrp.c (infer_value_range): Corresponding changes.
	* opts.c (default_options_table): Update due to option split.
	* gimple-ssa-isolate-paths.c: Fix trailing whitespace.
	(find_implicit_erroneous_behaviour): Pass additional arguments
	to infer_nonnull_range.
	(find_explicit_erroneous_behaviour): Similarly.
	(gate_isolate_erroneous_paths): Check both of the new
	options.

testsuite/

	* gcc.dg/pr38984.c: Use -fno-isolate-erroneous-paths-dereference.
	* gcc.dg/tree-ssa/isolate-2.c: Explicitly turn on
	-fisolate-erroneous-paths-attribute.
	* gcc.dg/tree-ssa/isolate-4.c: Likewise.

From-SVN: r205689