Arch Linux D package update

[Dicebot via Digitalmars-d-announce]

gdc

     - now uses 5.1 gcc base and 2.066.1 frontend
     - patched to correctly use system zlib library (resulted in 
linker errors before)

dtools

     - switched back to use dmd as default compiler

dub

     - switched back to use dmd as default compiler

dcd

     - new package, release 0.6.0
     - only x86_64 for now (upstream bug)
     - provides systemd service : `sudo systemctl enable 
dcd.service` to start automatically upon system startup
     - provides default /etc/dcd.conf with stdlib paths for Arch 
Linux