XeTeX with TeX fonts is only safe with ASCII input encoding (see #9740)
and we therefore force "ascii" when exporting with XeTeX and 8-bit TeX-fonts.
However, "utf8-plain" is a "power-user" option, which allows to switch off LyX's
encoding of the LaTeX file:
keep this also for "XeTeX with TeX fonts".
The user is responsible to ensure all characters can be processed and are
correctly shown in the output. The provided test sample shows the problems
with this encoding without special measures (like loading fontspec in the
user-preamble or a document class).
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]+
