[cl-markdown-devel] minor updates to cl-markdown

I've made several small tweaks to CL-Markdown in an effort to bring it a bit closer to its Perl cousin. In particular:

* I finally began to add to support for escaped characters (e.g., you can now say *hello* to output *hello*).

* Corrected a few edge cases and missing bits of support for links

* Many some very small improvements in the handling of Markdown coding with code blocks (it's not complete, but every step is a step).

As usual, CL-Markdown has a host of dependencies. You may want to try System-check to see what needs to be updated.