php: make curl wrappers optional

cURL wrappers are experimental and break any application/library
that rely on $http_response_header
ssh-agent: Don't have a timeout by default

IMHO, having a short timeout (1h) defeats the point of using
ssh-agent, which is not to have to retype passphrases all the time. Of
course, users who want timeouts can set programs.ssh.agentTimeout.

This restores the 14.04 behaviour.
Merge pull request #5383 from robberer/tmp1

php: make curl wrappers optional
xorg-server: enable DRI3 (close #5381)

TEST needed. I tested on my NixOS Thinkpad with Optimus nvidia and intel
cards.  Testing in other architectures is needed.

This patch also improves the regular expressions that scan the build
configuration files to enable the building of a binary utility in
xf86-video-intel: intel-virtual-output. This utility is useful for some
Optimus laptops

DRI3 was added to xorg-server propagatedBuildInputs so now it's inherited
by several projects that can use it.
nixos/virtualbox: Revert disable hardening.

This reverts commit 5d67b17901ff2c9a18647bd9453c6b0d4294b875.

The issues have been resolved by ac603e208c98b260db675fa0c13be94fa95216f4.

Tested this with hostonlyifs and USB support with extension pack.

Conflicts:
	nixos/modules/programs/virtualbox-host.nix

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Tested-by: Mateusz Kowalczyk <fuuzetsu@fuuzetsu.co.uk>
cabal-install: update to version 1.20.0.4

The test suite had to be disabled because of https://github.com/haskell/cabal/issues/2285.
ghc-head: fix configure phase to make sure the compiler knows how to use gmp properly

Start with version 7.9 of the compiler, the path to the gmp library must
now be passed to the top-level configure script.
ghc-head: bump version to most recent snapshot