Fix test error at test_bool_type_conversions()

nil cannot convert into Integer on ruby-1.9 or later.
(Intger(nil) => 0, on ruby-1.8)

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2526 f4f36d40-9719-0410-9868-dde021a23eda
Fix test error at test_ocptr_ary_assign() on ruby-2.x

use String#bytes not String[i] to getting integer byte value from
byte strings.

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2527 f4f36d40-9719-0410-9868-dde021a23eda
Add TODO comment for ruby-2.x compatibility Array#[]=

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2528 f4f36d40-9719-0410-9868-dde021a23eda