Moving xslthl files into a subdirectory

The highlighting-related stylesheets and XML config files now reside
in docs/xsl/highlight/ instead of just docs/xsl/.  Reduces clutter in
the docs/xsl/ directory.
Converting line endings in XSLTHL files

Had a mixture of DOS and UNIX line endings in different XSLTHL
highlighter files before this commit.  Converted everything to UNIX
line endings and normalized some of the indentation.
Reindent in custom DocBook XSL stylesheets
Fix XML version header in javascript-hl.xml
Moved AsciiDoc back matter into [appendix] tags
Modifying AsciiDoc-generated TOC depth
Minor AsciiDoc section metadata tweaks
Add tentative version compatibilty for 0.5.0
Change docs' Thunderdome references to Mogwai