Ruby 1.9 hash table and hash syntax

Reimplemented hash such that ```Hash``` preserves implementation order. Hash syntax was updated to Ruby 1.9 (```{a:1}```). See #189 for a performance benchmark and performance issues.

*Note:* These changes only work together with a modified GemStone version as some very basic Ruby classes are created in the C source code of GemStone (MagLev/HPI-GSS@matthias/ruby19).