Fix missing updates for lazy MacroData

Fix missing updates for lazy MacroData

Not all accessors did update the data previously. Therefore it could happen
that document export from the command line would output \newcommand, and from
GUI it would output \renewcommand for the same macro, simply because in the
GUI case the data was updated as a side effect of the GUI thread reading some
other member.
I also removed the mutable flag for requires_, since this member is always
set on construction and does not need any lazy update.