wheezy-stage4-lxde-edu: include pistore
various fixes to setup_spindle_environment

Using the $DEB_MIRROR from config doesn't work if you're building a raspbian
image (as that mirror only has armhf packages). Instead, always use
http.debian.net.

Makes a number of changes so that it can deal with the difference in schroot
1.4 as used in Ubuntu 10.04. Closes #115. Closes #130
wheezy-stage2: install firmware from untested repo for now
wheezy-stage3: use new tweaked memcpy etc
wheezy-stage4-lxde: import optimised pixman binary
wheezy-stage4-lxde-edu: add link to ocr pi resources
common: fix incorrect destination in ld.so.preload move
wheezy-stage4-lxde: fix optimised pixman setup
wheezy-stage3: install libfreetype6-dev needed for libraspberrypi-dev