message: Upgrade WASM Makefile to c++17.  No change in .wasm files.
diff: @@ -7,7 +7,7 @@ else
  endif
  %.wasm %.wat: %.cc ${API}/proxy_wasm_intrinsics.h ${API}/proxy_wasm_intrinsics.js
  - em++ -s WASM=1 -s LEGALIZE_JS_FFI=0 -s EMIT_EMSCRIPTEN_METADATA=1 --std=c++14 -O3 -g3 -I${API} --js-library ${API}/proxy_wasm_intrinsics.js $*.cc ${CONTEXT_LIB} -o $*.js
  + em++ -s WASM=1 -s LEGALIZE_JS_FFI=0 -s EMIT_EMSCRIPTEN_METADATA=1 --std=c++17 -O3 -g3 -I${API} --js-library ${API}/proxy_wasm_intrinsics.js $*.cc ${CONTEXT_LIB} -o $*.js
  wavm-disas $*.wasm $*.wat
  wavm-compile $*.wasm $*.wasm
  rm -f $*.js $*.wast
  