Make ml_progLib run type inferencer on each call

[myreen]

It would be nice to have process_topdecs fail immediately when given type-incorrect code to parse. This would be particularly helpful when developing code in basis, but is not generally desirable in the bootstrap translation.

I suspect this feature could be implemented by adjusting ml_progLib to keep track of the type inferencer state produced by the declarations that have been accumulated this far.

There needs to be a way to turn this feature off, e.g. by making the the type inferencer state information optional: NONE means that type inferencer is not run.

[IlmariReissumies]

It would also be nice to have an intermediate mode, where a warning is emitted but I'm allowed to move on with my life.