02d2cb5cc4
Expands the vector register allocator from 20 to 28 registers by including v8-v15. The HostToGuestThunk now saves/restores full Q8-Q15 (128-bit) instead of just D8-D15, and the GuestToHostThunk adds Q8-Q15 to its save/restore set since AAPCS64 only preserves their lower 64 bits across C calls. Reduces register pressure for VMX-heavy guest code at the cost of slightly larger thunk stack frames.