- Code cleanup patch from Dag-Erling Smorgrav, with compiler issue

- Code cleanup patch from Dag-Erling Smorgrav, with compiler issue
  fixes from FreeBSD's copy of Unbound, he notes:
  Generate unbound-control-setup.sh at build time so it respects
  prefix and sysconfdir from the configure script.  Also fix the
  umask to match the comment, and the comment to match the umask.
  Add const and static where needed.  Use unions instead of
  playing pointer poker.  Move declarations that are needed in
  multiple source files into a shared header.  Move sldns_bgetc()
  from parse.c to buffer.c where it belongs.  Introduce a new
  header file, worker.h, which declares the callbacks that
  all workers must define.  Remove those declarations from
  libworker.h.	Include the correct headers in the correct places.
  Fix a few dummy callbacks that don't match their prototype.
  Fix some casts.  Hide the sbrk madness behind #ifdef HAVE_SBRK.
  Remove a useless printf which breaks reproducible builds.
  Get rid of CONFIGURE_{TARGET,DATE,BUILD_WITH} now that they're
  no longer used.  Add unbound-control-setup.sh to the list of
  generated files.

git-svn-id: file:///svn/unbound/trunk@3137 be551aaa-1e26-0410-a405-d3ace91eadb9