- System images are not required for building. Disabling them makes building faster.
- Make ant flags configurable
Shut up annoying question to configure hardware profiles
Turn LD_LIBRARY_PATH into a suffix to allow NVIDIA's OpenGL driver to be used
Move kernelExtraConfig to common-config.nix (for x86)

It's bad to have the kernel config scattered across two places.  (This
should also be done for the other architectures.)

Also, restore Xen and KVM guest support in Linux 3.10.
VM builds: Use the default kernel
VM builds: Reduce kernel verbosity
git: Update to 1.8.3.4
git: Install git-subtree
git-subtree: Remove

This package is obsolete because it's now part of git (see
https://github.com/apenwarr/git-subtree/blob/master/THIS-REPO-IS-OBSOLETE).