* Fix Pacman regex for unmatched Arch package name
`ansible -m pacman -a upgrade=yes $(hostname)` failed due to not
accounting for the `+` character in the `pacman -Qu` output line:
libsigc++ 2.10.0-1 -> 2.10.1-1
Per the Arch wiki¹, package names can contain alphanumeric characters,
and any of {`@`, `.`, `_`, `+`, `-`}.
The existing `re` covered `_` (part of `\w` in Python), and `-`
(explicitly included). This change adds `@`, `.`, and `+` (in
ASCII-betical order).
¹: https://wiki.archlinux.org/index.php/Arch_package_guidelines#Package_naming
* Add explanation for `pacman -Qu` regex matching
* Remove unneeded non-capturing groups in regex
73a7a0877d