How can I make global environmental changes for individual subsystems?
It may sometimes be necessary to change environmental parameters for individual subsystems, such as changing the INCLUDE_PATH or defining new global functions, and this can now be done by means of a file called include.subsystem.inc which can be created in the top-level directory for each subsystem. This file, if it exists, will be processed during the inclusion of include.general.inc which in turn is referenced on the very first line of each page controller.