handle simple bashisms:

- [[ ]] -> [ ]
- == -> =
- source -> .
- redirect of fd 200 is error in mksh, use fd 9
- &> /dev/null -> > /dev/null 2>&1
- useless function keyword
- echo -e -> printf

still left bash shebang which did not validate with checkbashism, mostly
due 'type' being reported as bashism

Signed-Off-By: Elan Ruusamäe <glen@delfi.ee>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>