Pacman (Arch Linux) package manager dependency parser

[cr0hn]

Add support for the pacman package manager used by Arch Linux distributions.

As with the others package manager there is a need to try to map as closely as possible from package name to CPE prior to search for vulnerabilities.

Try to use the same approach; look for installed packages and run the CVE search against them or get a list of the desired packages to search for in stdin.