Darwin/x86_64: Fix 64/32 size shortening warnings
Darwin/aarch64: Use CNAME refs like arm32.
Darwin/aarch64: Restrict .size to ELF like arm32.
Darwin/aarch64: Account for long double being equal to double
Darwin/aarch64: Fix "shadows declaration" warnings
Darwin/aarch64: Fix size_t assumptions
Darwin/aarch64: Respect iOS ABI re: stack argument alignment