Incorrect behaviour of cffi build step for deeply nested modules (nesting level > 1)

[daa]

First, thank you for milksnake, I found it very helpful in building external libraries with setuptools.

Here is a problem I've met: consider cffi module named p0.p1.modname, currently CffiModuleBuildStep determines module base as p0 and consequently puts compiled library and generated cffi module in build/lib/p0 directory instead of correct build/lib/p0/p1 and thus required module cannot be found and imported.