unifdef(1) on Linux
The text 92b135a50b86, as Debian 7 (Wheezy) shipped it.
remove preprocessor conditionals from code
Flags it lists
-
-B -
-D -
-I -
-K -
-S -
-U -
-V -
-b -
-c -
-d -
-e -
-iD -
-iU -
-k -
-n -
-o -
-s -
-t