boost: Add optional Boost.MPI support

Boost.MPI is a C++ interface library to the
message passing interface (MPI) standard.
android-ndk: r9d -> r10c
Removed duplicate
ghostscript: drop GNU fork and update
qpdf: add package
ijs: add package
cups: update package
cups-filters: add package
epdfview: fix building with cups 2.0
pycups: update package
kernel: 3.10.59 -> 3.10.60
kernel: 3.2.63 -> 3.2.64
kernel: Remove 3.17 buildfix
kernel: Remove 3.15
Actually remove linux_3_15
nixos/unifi: Remove old ROOT.war links before relinking
foomatic-filters: fix building with cups-2
strongswan: bump
vim: improve *.nix plugin (#4662)

- Sync syntax from source.
- Add indentation conventions.
cmus: update from 2.5.0 to 2.6.0

Adds CUE and pulseaudio support