libpcap: pass --with-pcap=linux for all linux systems

...instead of just for i686-linux.

Without a --with-pcap= configure flag, the build system tries to
auto-detect the backend by poking in /dev, /usr/include etc... In the
pure nix world, this auto-detection fails. (Good, we don't want host
details to leak into the build.)

The end result of this (failed) auto-detection; no packet capture
possible:

  $ sudo tcpdump -i wlp2s0
  tcpdump: live packet capture not supported on this system

This fixes the above issue on 64-bit linux systems, and probably other
architectures supported by linux.
kernel: 3.10.56 -> 3.10.58
kernel: 3.12.29 -> 3.12.30
kernel: 3.14.20 -> 3.14.22
kernel: 3.16.4 -> 3.16.6
kernel: 3.17 -> 3.17.1
kernel: 3.2.62 -> 3.2.63
kernel: 3.4.103 -> 3.4.104
kernel: Fix missing ;
git-annex: temporary patch to build the current version
Elm: no longer references pandoc
haskell-hakyll: Allow it to build again
haskell-yi: make the wrapper less cumbersome

It still suffers from ‘everything breaks’ if there is any Haskell in
user env: https://github.com/NixOS/nixpkgs/issues/4560