Push

A couple of new features in Clojush.

Available as usual from: https://github.com/lspector/Clojush

20110118: - Added support for tagged_code_<number> instructions. These are like
            tagged_<number> instructions except that retrieved values are pushed
            onto the code stack rather than the exec stack. Without these the
            only way to get tagged values onto the code stack is to wrap
            values with code_quote prior to tagging. An alternative approach
            is to add new tagging instructions that automatically perform
            code_quote wrapping, but for full generality that would require
            new instructions for each type; also quote-tagged values would
            always be destined for the code stack, while the scheme adopted
            here allows any stored value to be retrieved either to exec or to
            code.
          - A value of 0 for the evalpush-time-limit parameter of pushgp
            now means that no time limit will be enforced. This is also
            now the default.