CacheInterface.h: make CkCache.h an angled #include

Needed for similar reason as described in commit @c9a512e: ChaNGa's
dependency generation assumes that CkCache.h is a local include, and here
the files _it_ includes were being listed without path in Makefile.dep.
Merge pull request #4 from insaneinside/build-system-fixes

CacheInterface.h: make CkCache.h an angled #include