When called from mailboot.service, the systemd-analyze output was missing
because systemd-analyze print the following line on stderr (not in mail):
Bootup is not yet finished. Please try again later.

To workaround this, we will test systemd-analyze during a configurable time.
If systemd-analyze is not ready at the time left, the information will be
ignored.

systemd unit type is now Tyep=idle, to:
- don't block (particulary when waiting systemd-analyze)
- we don't need to be executed fastly (we can be more fair than Type=simple).

- arch depends of dist
- PKGBUILD depends of configure (version is set inside)

As a consequency, this patch also add a config file for mailboot.

Add PKGBUILD installation how to
Add using how to
Add AUR link

This will make github display RestructuredText correctly.

This is not used (and will no be)

There is currently no state in bootmail script which require to have the service
marked as running in systemd.

All the basics should be here.