Initial support for x64 windows calling convention on the single pass compiler

[Pombal]

Hello, I started implementing some of the changes @losfair mentioned in this issue: #347

Some simple functions already work but more complicated ones do not. An example of a function that doesn't work is double_then_add below:

(module
            (func $multiply (import "env" "multiply") (param i32 i32) (result i32))
            (func (export "add") (param i32 i32) (result i32)
               (i32.add (local.get 0)
                        (local.get 1)))
            (func (export "double_then_add") (param i32 i32) (result i32)
               (i32.add (call $multiply (local.get 0) (i32.const 2))
                        (call $multiply (local.get 1) (i32.const 2))))
        )

This probably has to do with proper handling of the 32 byte shadow space which I haven't added.
emit_call_sysv in codegen_x64.rs would have to be modified for this to work but the code has changed. @losfair mentioned a CONSTRUCT_STACK_AND_CALL_WASM which doesn't seem to exist anymore.

Ideally a maintainer would take this proof of concept and complete it. But with some guidance on better workflows for debugging the generated code on windows I can implement the missing functionality.

[webmaster128]

Can this be closed after #2574 was merged?