* stringpool.cc (Stringpool_template::Stringpool_template): Initialize
offset_.
(Stringpool_template::new_key_offset): New method.
(Stringpool_template::add_string): Assign offsets when adding new
strings.
(Stringpool_template::set_string_offsets): Do not set string offsets
when not optimizing.
* stringpool.h (Chunked_vector::Chunked_vector): Initialize data
member size_.
(Chunked_vector::clear): Clear size_.
(Chunked_vector::reserve): Call reserve method of all Element_vectors.
(Chunked_vector::size): Return size_.
(Chunked_vector::push_back): Use size_ to find insert position.
(Chunked_vector::size_): New data member.
(Stringpool_template::set_no_zero_null): Assert string set is empty.
(Stringpool_template::new_key_offset): New method declaration.
(Stringpool_template::offset_): New data member.
* stringpool.h (class Stringpool_template): Add optimize_ field.
(Stringpool_template::set_optimize): New function.
* stringpool.cc (Stringpool_template::Stringpool_template):
Initialize optimize_ field.
(Stringpool_template::set_string_offsets): Test local optimize
fild rather than parameter.
* layout.cc (Layout::Layout): Call set_optimize on the section
name stringpool.
array size plus one.
(Stringpool_template::set_string_offsets): Subtract one from key
before using it as an array index.
(Stringpool_template::get_offset_with_length): Likewise.
(Stringpool_template::write_to_buffer): Likewise.
* stringpool.h (Stringpool_template::get_offset_from_key):
Likewise.
