allow build path spaces in support scripts

The first three bullets originate from #252.  Hopefully I broke the commits out correctly this time.
- allow build path spaces in configure & support scripts
- use the same die function for all scripts
- error check argument passed into epgdump
- use `http` URL instead of `git` for cloning dtv-scan-tables git repo
  - this allows `./configure` to not hang when ran behind a firewall