Emacs: Adjust org-mode.

- Show whole content of a matching sparse tree.  This is mainly for
LaTeX exporting convenience.

- Properly hide leading stars

- Use XeLaTeX for LaTeX PDF exporting.  Adjust macro packages accordingly.
Emacs: Properly load AucTeX from EPLA.
Emacs: Set timeout for Company async operations.
Emacs: Move some more packages to their EPLA version.