When upgrading-downgrading from one asterisk version to another, you may
need to edit config files.
For instance, when upgrading sip.conf from 1.4 to 1.8, it is tempting to use
a single common file and add some #ifdef-like statements in it so that
1.8-specific statements are not mixed with 1.4 statements.
What are the best practices and tools for this ?