As far as I know, we don't implement the proposal at all.
```
spacetanuki% wasm2wat --enable-all data.28.wasm
(module
(memory (;0;) 1)
(data (;0;) (i32.const 42
i32.const 0
i32.sub) ""))
spacetanuki% toywasm --load data.28.wasm
spacetanuki% ~/git/wasm-micro-runtime/product-mini/platforms/darwin/b.classic/iwasm data.28.wasm
WASM module load failed: illegal opcode or constant expression required or type mismatch
spacetanuki%
```
data.28.wasm in the above example is a binary version of:
https://github.com/WebAssembly/extended-const/blob/8d4f6aa2b00a8e7c0174410028625c6a176db8a1/test/core/data.wast#L184-L187
This should guarantee that the various macros required by
wasm_proposal.c are defined even if the build system does not supply
them to the compiler command.
