Init script executable check should be smarter about permissions

[jheiss]

Situation:

Init script permissions don't appear to allow root execution. I.e. script is owned by user "foo" and has 0700 permissions. In this case tpkg will warn that the script is not executable, even though root will still be able to execute it (by virtue of being root).

Need to confirm that the behavior of root executing things with any sort of execute bit set is fairly universal across Unix variants, then modify the permissions check in tpkg to account for that fact.

Was: https://sourceforge.net/apps/trac/tpkg/ticket/35