Use implicit rules rather than $(eval ...).
Generate into into www.mlton.org/, rather than wiki/.
Generate into both www.mlton.org/ and localhost/.

These two destinations will have distinguished formatting.
Differentiate documentation for www.mlton.org and for localhost.
Factor AsciiDoc configuration into components for markup and for html5.
Disable AsciiDoc special section titles.

AsciiDoc's "special section titles" auto-magically map predefined
section titles to specific markup templates.  This is a deprecated
feature (better handled by explicit section markup templates), but
there appears to be no mechanism to globally disable special section
titles.

Instead, explicitly delete each special section title added by
lang-en.conf.
Force English language.
Always use $(ASCIIDOC) for asciidoc program.
Update .gitignore files.

Limit patterns to files in same directory as the corresponding
.gitignore file.
Limit 'all' target to documentation for localhost.

Documentation for www.mlton.org shouldn't be built by default (since
default corresponds to end-user source build and install).
Include .flags files in corresponding _DEPS variables.
mlton-gcse.js is not required for localhost documentation.
Use asciidoc and dblatex to generate mlton-guide.pdf.
Build and install AsciiDoc-based guide.