Adjust tex2lyx InsetArgument to format 446

tex2lyx does now allow mixed order of required and optional arguments.
Do not compile trivstring.cpp if not needed

This avoids a MSVC warning.
Move cjk check out of the loop

According to the indentation this was probably a merge error, and the check is
only needed once.
Parse starred InsetLayout correctly

Previously, an InsetLayout was not found if the LaTeX name was starred, e.g.
for "\caption*".
whitespace
Remove InsetArgument 999 workaround

Since we iterate through all arguments we can as well compute the correct id
directly.