Pass all include directories through clang

It turns out I was only passing the last include directory through
clang into pinclude as opposed to all of them.  This fix is simple --
I just have a fixe array of 1024 include directories inside the clang
translation unit structure which all get passed.

This fixes a bug where some headers aren't getting picked up.
Specifically it was generated headers, but the problem would manifest
whenever there were multiple include directories.