IMHO there is abug in grammar-fw.texi which breaks the make-process - at least with some makeinfo versions (i'm using GNU makeinfo 4.2).
There is in line 154:
And the texinfo-manual says: When creating info-file per default the file grammar-fw-ov.txt will be searched. ==> because this file does not exists the makeinfo fails and stops.
When encapsulation this image within a
then running makeinfo and creating info-files ignores this image which is what shoud be done.
If you have no ojections i will commit these changes today afternoon.