So this has just been fixed in unstable, and will be available in tomorrrow’s snapshot package.
To summarize, you need to do something of the order of the following in Matlab:
>> xy='/path/to/dir/with/other/modfile/';
>> dynare modfile.mod -Dpath=xy
and then, in your modfile, you’ll have:
@#define othermodfile=path+'othermodfile.mod'
@#include othermodfile