Add Lazy K backend

[woodrush]

This pull request adds a backend for Lazy K.

Similar to the Binary Lambda Calculus backend in #118, this backend also uses LambdaVM to implement the virtual machine. This is done as follows:

• LambdaVM is compiled to a SKI combinator calculus term using the contents of LambdaVM's repo.
• The differences in the I/O encoding is absorbed by adding an encoder-decoder layer.
  • LambdaVM expects I/O to be encoded as a list of bits as explained in #118. On the other hand, the Lazy K interpreter encodes them as Church Numerals, and also encodes EOF as an infinite list of 256s. The encoder-decoder layer translates these differences when receiving and returning I/O to and from the Lazy K interpreter.

The Interpreter

This backend uses @irori's Lazy K interpreter. It automatically clones and compiles it in tools/runlazy.sh.

Tests

I've confirmed that running the test make lazy takes about 3 minutes on my machine.

Some tests that take a lot of time are left out from make lazy. Omitted tests are included in make test-lazy-full. I expect make test-lazy-full to run successfully for the following reasons:

• All of the programs included in make lazy runs successfully.
• The Lazy K backend and the BLC backend in #118 are both based on LambdaVM. Since The BLC backend runs make test-blc-full successfully, I expect the same holds for the Lazy K backend as well.

[woodrush]

I've just confirmed that running make test-lazy-full finishes in about 4 minutes on my machine.

[shinh]

Resolved the conflict and merged. Thanks!