* fileread.cc: (File_read::View::~View): Use the new

	* fileread.cc: (File_read::View::~View): Use the new
	data_ownership_ filed.
	(File_read::~File_read): Dispose the new whole_file_view_.
	(File_read::open): Mmap the whole file if needed.
	(File_read::open): Use whole_file_view_ instead of contents_.
	(File_read::find_view): Use whole_file_view_ if applicable.
	(File_read::do_read): Use whole_file_view_ instead of contents_.
	(File_read::make_view): Use whole_file_view_ instead of contents_,
	update File_read::View::View call.
	(File_read::find_or_make_view): Update File_read::View::View
	call.
	* fileread.h: (File_read::File_read): Initialize whole_file_view_,
	remove contents_
	(File_read::View::Data_ownership): New enum.
	(File_read::View::View): Replace bool mapped_ with Data_ownership
	argument.
	(File_read::View::mapped_): Remove (replaced by data_ownership_).
	(File_read::View::data_ownership_): New field.
	(File_read::contents_): Remove (replaced by whole_file_view_).
	(File_read::whole_file_view_): New field.
	* options.h (class General_options): Add --keep-files-mapped.