Add gsub() from Shell Scripting Recipes - Chris F.A. Johnson (c) 2005
Load MOVED when starting build into tmpfs /poudriere/MOVED/cat_port file containing new origin
Fix packages returning old origins by checking MOVED.

This fixes a recent package build failure with qt4 where dependencies
were not properly determined due to partial sanity checks. By tracking
MOVED, the dependencies are again proper.
Also track MOVED origins of package dependencies for the 'new dependency' incremental rebuild