auxiliary: ship all files in the distribution tarball

auxiliary: ship all files in the distribution tarball

 - Add all headers into Makefile.sources
 - Don't forget the target-helpers
 - Add the python scripts & the formats table/list (csv)
 - Temporary add vl/vl_winsys_dri.c to EXTRA_DIST until we rework the
way VL is build.
 - Add the following to EXTRA_DIST - they are included via the
generated u_indices_gen.c thus we should not add them to *SOURCES.
  indices/u_indices.c
  indices/u_unfilled_indices.c

XXX: Should we nuke gallivm/f.cpp ? It seems that no-one is using it.

v2: Rebase

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>