Added subprocess32 to dependencies build process.
Added subprocess32 to dependencies build process.

The subprocess32 module is a backport of the subprocess module from Python 3.2 to Python 2.6/7. We need it because the standard Python2.7 subprocess module is fundamentally broken, and can deadlock if used in a multithreaded application. Although we generally install additional python modules in $GAFFER_ROOT/python so it's very clear what additional python modules are available, I've installed this one in the depths of the standard lib/python2.7/site-packages directory, since it seems best to think of it as part of the standard python install.

andrewkaufman/gaffer,chippey/gaffer,appleseedhq/gaffer,ivanimanishi/gaffer,johnhaddon/gaffer,hradec/gaffer,hradec/gaffer,appleseedhq/gaffer,lucienfostier/gaffer,appleseedhq/gaffer,johnhaddon/gaffer,chippey/gaffer,johnhaddon/gaffer,ImageEngine/gaffer,hradec/gaffer,andrewkaufman/gaffer,goddardl/gaffer,boberfly/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,goddardl/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,goddardl/gaffer,ImageEngine/gaffer,chippey/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,chippey/gaffer,ivanimanishi/gaffer,boberfly/gaffer,hradec/gaffer,goddardl/gaffer,boberfly/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,ivanimanishi/gaffer,ivanimanishi/gaffer,ImageEngine/gaffer,boberfly/gaffer,GafferHQ/gaffer,appleseedhq/gaffer,hradec/gaffer