[arch-general] Change Arch's default crond

[Sven-Hendrik Haase]

We all know the situation with dcron (it can't keep time properly) and
it still is broken. No fix (or any changes for that matter) have gone
into its upstream git for over a year now. There have been multiple
yeah-I'll-take-a-looks from various people as well as its upstream
maintainer and no work was done.

I certainly don't want to offend anybody but I think it is time another
crond was made quasi default by swapping it for dcron in base group. I
know that users can do that themselves but the we shouldn't suggest
packages we know are broken by putting them into the base group. Perhaps
fcron is a fine choice.

Bug report for reference: https://bugs.archlinux.org/task/18681

-- Sven-Hendrik