Don't highlight deprecated + line-break, highlight new style \ line-break.
Documentation updates.
Implemented 'inclusion' macro invocation.
- Allow 'inclusion' macro invocation to prefix block elements.
- Document 'inclusion' macro invocation.
- rimuc: Added MathJax support for --styled option. Enabled by defining
  non-blank {mathjax} macro value.
- rimuc: --styled option Highlight.js support enabled by defining
  non-blank {highlightjs} macro value.