BUILD: Create engines/ dir if necessary, to fix out-of-tree builds
DEVTOOLS: Factor out function to create directories in create_project.
DEVTOOLS: Adapt create_project to create engines/ dir if necessary
BUILD: Add code to maintain ordering of engines in generated files.

This is mainly "cosmetic" to keep the SCUMM engine and subengines at
the top of the various files, but probably a good idea to prevent any
subtle regressions associated with changing the order.
DEVTOOLS: Make create_project sort SCUMM as first engine.

This makes create_project output consistent with configure output again.
(See 33c1ffd073821a68e20bed6e4c257aed7ed66401 for the configure change).