Also adds a new INSN_MODE_INVALID for 0 to catch uninitialized values.

I found this neat trick in llvm output, and the existing code was broken
anyway.

ir: Use mode_is_float()/mode_is_int() instead of get_mode_sort()/->sort == irms_float_number/irms_int_number.

There are still similar problems left.

* This corrects the requirements of fStore.

This properly models the data dependencies and avoids keep edges.

Determine the pos from the node to push.