Makefile.in: Makefile depends on Makefile.in

To regenerate Makefile, we use `config.status` (which re-runs `configure`
with all user-provided options).
configure{,.ac}, Makefile.in: added support for out-of-source builds
Makefile.in: add source and build directories to C include path, too
ParallelGravity.h: made liveViz.h an angled #include

Without this, Charm's dependency-generation was listing "liveViz.h" --
without path -- as a dependency for any object build from a source that
includes ParallelGravity.h.  Since liveViz.h is found via path search
(and is not kept in the local directory), this is the right include style
to use for it anyway.
Merge pull request #3 from insaneinside/build-system-fixes

Build system fixes: this looks OK now, so I'm merging.