ARM64 Darwin Improvements

Update goffi v0.3.6 → v0.3.7

Improved

• Comprehensive ARM64 Darwin support — tested on M3 Pro hardware
• Nested struct handling — proper layout for complex struct types
• Mixed integer/float struct support — automatic struct layout computation
• Struct returns 9-16 bytes — Call8Float now returns both X0 and X1 registers

Fixed

• Segmentation fault in string output benchmarks on Darwin

Contributors

• @ppoage — ARM64 Darwin implementation, Objective-C test suite, assembly verification