Make Array#[]= raise IndexError.

If second param is negative, Array#[] raise IndexError.
Replace from include <>, to include "".
Merge pull request #2208 from yui-knk/array-error

Make Array#[]= raise IndexError.
Merge pull request #2209 from yui-knk/fix-include

Replace from include <>, to include "".
use mrb_field_write_barrier_value() in array.c
use mrb_field_write_barrier_value() in hash.c
fix typo
Merge pull request #2210 from yui-knk/fix-typo

fix typo