Import mt-daapd from AUR

https://aur.archlinux.org/packages/mt-daapd/
mt-daapd: Update package for /usr/sbin -> /usr/bin move
mt-daapd: Fix creation of cache dir

mt-daapd needs /var/cache/mt-daapd, so let's create it (and make
sure the permissions are nobody:nobody too, since the default conf
wants to run as nobody).
mt-daapd: Split build() and add package()

makepkg likes to have a package() function.  Splitting the building
and packaging functionality makes sense.
mt-daapd: Update package() function to use more readable logic for failure detection
mt-daapd: Quote variables just in case
dmapd: Quote variables and remove unneccessary ${var} notation
dmapd: Fix another unneccessary variable notation
mt-daapd: Simplify packaging and increment to 0.2.4.2-9

We're already inside the source folder, no need to specify the path
every time.