Simplify the logic for language package selection and make it more consistent:
Use polyglossia with non-TeX fonts (system fonts/Unicode fonts) for all
export flavours (XeTeX, LuaTeX, DVI-LuaTeX), if the language package setting
is "auto" and there is no language not supported by Babel and no package
providing Babel.
This solves some Babel-related autotest cases and leads to some new failures
due to the polyglossia language nesting problem.
Comment by Günter Milde:
Actually, *all* Spanish manuals either fail or have wrong output with
Unicode TeX engines and 8-bit fonts. The reason is known: a bug in Babel
that uses utf8 strings whenever Xe- or LuaTeX is detected.
Always-Babel now set in the example document.
Adapted the autotest categorization:
* fails for some developers (why?)
* wrong output with pdflatex/LuaTeX and DVI (missing landscape slides).
and introduce sublabels
Sublabels section in *.Tests starts with 'Sublabel: name'
and is valid until start of a new sublabel.
'name' contains only ascii characters [a-z]+
