I'd like the makefiles to be able to regenerate src/trunnel/*.[ch] from src/trunnel/*.trunnel as needed or on demand. This is a little nontrivial, since we'd need the following: * A way to detect trunnel of the appropriate version. * Actual meaningful version numbers on trunnel. * A way to not require developers to have trunnel installed. * Support for out-of-tree builds (which can get really hard with generated code, and even harder with optionally generated code).