audit: suggest proper `if build.with(out)` usage

The current check on `unless build.with(out)?` is missing the option and doesn't negate with/without. This change brings in the relevant option and suggests a logically equivalent `if build.with(out)?`. It detects symbols, but doesn't add double quotes to strings. Not sure about the best wording.

Before:
```
nlopt:
 * Don't use unless with 'build.with': use 'if build.with?'
 * Don't use unless with 'build.with': use 'if build.with?'
 * Don't use unless with 'build.without': use 'if build.without?'
```
After:
```
nlopt:
 * Use if build.without? 'octave' instead of unless build.with? 'octave'
 * Use if build.without? :python instead of unless build.with? :python
 * Use if build.with? :python instead of unless build.without? :python
```