Add missing size declarations for 8-byte registers.

Add missing size declarations for 8-byte registers.

This fixes the coercion from IND_ALL_D to FREG.  The coercion had
never happened, because IND_ALL_D had 8 bytes but FREG had 4 bytes.
Instead, ncg always stacked the IND_ALL_D and unstacked a FREG.  The
stacking rule uses f0, so the code did load f0 with the indirect
value, push f0 to stack, load f1 to stack, move stack pointer.  Now
that FREG has 8 bytes, ncg does the coercion, and the code just loads
f1 with the indirect value.