Don't depend on tpike if RUNPIKE is used, and use precompile.sh instead of
tpike directly to allow making of autogenerated source without tpike. Also
updated some rules due to necessary changes in precompile.sh behavior. Did
away with some obsolete crud in the "all" target. Split off a "source"
target from "export" to allow source generation without version bumping etc.
More efficient regeneration of the Makefile after make depend.