Control characters are not escaped when emitUTF8 = true

[TheStormN]

Describe the bug
In JsonCPP 1.9.2. There is a configuration option emitUTF8 which can be used to force the library to not escape UTF-8 characters. However, when using it, the control characters are also not escaped which breaks the output json string and other software have issues parsing it. Currently to get non-escaped UTF-8 with escaped control characters, I had to downgrade to 1.8.3.

To Reproduce

Json::Value root(Json::objectValue);

root["unprintable"] = std::string{0x01, 0x02, 0x03, 0x10};

Json::StreamWriterBuilder builder;
builder.settings_["emitUTF8"] = true;
auto result_str = Json::writeString(builder, root);

Expected behavior
The result_str should be "{"unprintable":"\u0001\u0002\u0003\u0010"}" but I get the same characters as in the input string.

Desktop (please complete the following information):

• OS: Windows 10
• Meson - no idea, I'm using Conan
• Ninja version - no idea, I'm using Conan

Additional context
Version 1.8.3 does not suffer from that issue.

[TheStormN]

Ok it seems that it was easy to fix that bug. I submitted a PR. @dota17 @BillyDonahue It would be nice if we can get a new release with that fix, so I'll be able to fetch it from Conan and get back to the latest version. :)