Passthrough is usable now. There have been issues with the `access`
operation: it's unclear what it must return, since the answer isn't
known at the time when it is called. If it always returns "denied", many
applications would finish without trying to open a file, thinking the
access would not be granted after `access` call. Although always
returning "permitted" seems like a better choice, it still might cause unexpected
behaviour. Perhaps one way to solve this, is actually asking user
whether to allow access. In any case, this issue needs to be looked
into.
Now source files handling is delegated to functions defined
in `sourcefs.c` file. By encapsulating methods for managing
the underlying source files structure we ensure that all
code changes to the source file protection strategy will be
localized to `sourcefs.c` file.
Also changed Makefile to use more sane way of handling
options and build flags.
