TODO:
- struct return values
- support for unions in signatures
- more testing
- complex types
- packed structs
- writing structs to buffers (useful and we have most of the machinery).
Add support for integer return and floating point return variants, as
well as arguments on the stack. Start flushing out struct arguments.
Still needed:
- structs (packed and unpacked)
- complex numbers
- long doubles
- MASM alternative for windows (you can technically use sysv abi on
windows)
- more calling conventions.
