wasm-decompile: Fix unescaped characters in data output. (WebAssembly…

…#2500)

Characters `"` and `\` which have special meaning in data
representations are not escaped by wasm-decompile and are passed to
output as is.
This PR fixes such incorrect behavior.
All tests still pass (although no cases are added).

src/decompiler.cc

@@ -702,7 +702,7 @@ struct Decompiler {
     size_t line_start = 0;
     static const char s_hexdigits[] = "0123456789abcdef";
     for (auto c : in) {
-      if (c >= ' ' && c <= '~') {
+      if (c >= ' ' && c <= '~' && c != '"' && c != '\\') {
         s += c;
       } else {
         s += '\\';