-------------
1 bug fix, a few tweaks, one new feature

rename `version[]` to `markdown_version[]`

 1. Don't \\-escape every character, just the characters that might
    have special meaning to markdown.
 2. Specialcase the entity `�` -- use it as a non-spacing token break.
 3. Clean up the `EXPAND()` macro to have an explicit execution order.
 4. Detect the presence of the vile loathsome gcc compiler.

Add the output flag **`MKD_CDATA`**, which tells markdown to generate
output suitable as data inside a generic xml document.