Replace from include <>, to include "".
Make sure c is large enough if there is an overflow
Consolidate muliptlication into one place
Merge pull request #2247 from yui-knk/fix-include

Replace from include <>, to include "".
Merge pull request #2248 from carsonmcdonald/mulfix

Another change to fix issue #2244
Add ISO No. to Integer#divmod  test.
Merge pull request #2249 from yui-knk/fix-iso

Add ISO No. to Integer#divmod  test.