Fix a bug on multiple versions of define_type_raw
Fix a bug on multiple versions of define_type_raw

In Hol-light, this function is defined multiple times in an incremental
manner (the later calls the former).
Porting to F#, we use recursive references to the same value leading to
infinite recursion.

This mistake doesn't seem to occur with other multiple-version
functions.

jack-pappas/NHol