Loading ifc.ifc_buf using the new tor_free() causes undefined behaviour on x86_64 macOS

On macOS x86+64, the new tor_free() from legacy/trac#24337 (moved) loads ifc.ifc_buf, which leads to undefined behaviour. ifc.ifc_buf is a char * which should be aligned to a multiple 8 bytes, but it is always aligned at 8-bytes (ifc on the stack) plus 4 bytes (ifc_len and pragma pack(4)).

This bug was caused by legacy/trac#24337 (moved), which has been merged to master (0.3.3.0-alpha-dev), and Apple's 32/64 bit kernel data structure compatibility code.

It was discovered using our unit tests and clang's address sanitizer.

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