* Makefile.in (PREPROCESSOR_DEFINES): Add
	@TARGET_SYSTEM_ROOT_DEFINE@.
	* configure.in (PREFIX_INCLUDE_DIR): Don't define if $with_sysroot
	is specified or if building a cross compiler.
	(TARGET_SYSTEM_ROOT_DEFINE): Add TARGET_SYSTEM_ROOT_RELOCATABLE
	if the sysroot is under $exec_prefix.
	* configure: Regenerated.
	* cppdefault.h: Use native include paths if TARGET_SYSTEM_ROOT is
	defined.
	(struct default_include): Add add_sysroot field.
	(cpp_SYSROOT): Declare.
	* cppdefault.c (cpp_include_defaults): Fill in add_sysroot
	field.
	(cpp_SYSROOT): New variable.
	* cppinit.c (cpp_create_reader): Initialize
	CPP_OPTION (pfile, sysroot).
	(init_standard_includes): Handle add_sysroot.  Do not
	add unrelocated copies of relocated directories.
	(COMMAND_LINE_OPTIONS): Add -isysroot.
	(cpp_handle_option): Handle -isysroot.
	* cpplib.h (struct cpp_options): Add sysroot member.
	* gcc.c (The Specs Language): Update description of %I.
	(target_system_root_changed): New variable.
	(process_command): Conditionalize make_relative_prefix call
	on !VMS and TARGET_SYSTEM_ROOT_RELOCATABLE.  Set
	target_system_root_changed.
	(do_spec_1): Add -isysroot to %I.
	* doc/invoke.texi (Spec Files): Update description of %I.
	* doc/install.texi (--with-sysroot): Update comment about
	relocation.

From-SVN: r62853