Fix missing assign value to ENCINDEX_RUBYCOCOA_UNKNOWN

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2561 f4f36d40-9719-0410-9868-dde021a23eda
Fix test_ocptr_as_id fails on ruby-2.x

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2562 f4f36d40-9719-0410-9868-dde021a23eda
Fix "Symbol not found: _init_encoding_conversion" on ruby-1.8

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2563 f4f36d40-9719-0410-9868-dde021a23eda