Cleanup and simplify handle_interface_command:

- Reduce indent: invert logic of strcmp test.
- Reduce scope: declare variables upon first use in loops.
- Reduce unsaid: compare end of table with NULL.
- Remove superfluous braces around blocks with one statment.
- Improve language that introduces the list of built-in drivers.


git-svn-id: svn://svn.berlios.de/openocd/trunk@2128 b42882b7-edfa-0310-969c-e2dbd0fdcd60