Add initial support for anyref as an opaque type (#2294)

Another round of trying to push upstream things from my fork.

This PR only adds support for anyref itself as an opaque type. It does NOT implement the full [reference types proposal](https://github.com/WebAssembly/reference-types/blob/master/proposals/reference-types/Overview.md)--so no table.get/set/grow/etc or ref.null, ref.func, etc.

Figured it was easier to review and merge as we go, especially if I did something fundamentally wrong.

***

I did put it under the `--enable-reference-types` flag as I imagine that even though this PR doesn't complete the full feature set, it probably is the right home. Lmk if not.

I'll also be adding a few github comments to places I want to point out/question.

1 files changed, 1 insertions, 0 deletions

diff --git a/test/example/c-api-kitchen-sink.c b/test/example/c-api-kitchen-sink.c
index 661d04ce2..3d9d42fa1 100644
--- a/test/example/c-api-kitchen-sink.c
+++ b/test/example/c-api-kitchen-sink.c
@@ -155,6 +155,7 @@ void test_types() {
   printf("BinaryenTypeFloat32: %d\n", BinaryenTypeFloat32());
   printf("BinaryenTypeFloat64: %d\n", BinaryenTypeFloat64());
   printf("BinaryenTypeVec128: %d\n", BinaryenTypeVec128());
+  printf("BinaryenTypeAnyref: %d\n", BinaryenTypeAnyref());
   printf("BinaryenTypeExnref: %d\n", BinaryenTypeExnref());
   printf("BinaryenTypeUnreachable: %d\n", BinaryenTypeUnreachable());
   printf("BinaryenTypeAuto: %d\n", BinaryenTypeAuto());