Split declarations and definitions to improve compile times when editing (#13332)

* Split FileStream declarations and definitions

* Split JobPool declarations and definitions

* Split StringBuilder declarations and definitions

* Split StringReader declarations and definitions

* Split ZoomLevel declarations and definitions

* Fix missing include in FileClassifier.cpp

* Remove pragma once from source files

* Fix missing include in StringBuilder.h

* Update Xcode project

* Fix compilation of tests

Co-authored-by: Michael Steenbeek <m.o.steenbeek@gmail.com>

src/openrct2/core/StringReader.cpp

@@ -0,0 +1,58 @@
+/*****************************************************************************
+ * Copyright (c) 2014-2020 OpenRCT2 developers
+ *
+ * For a complete list of all authors, please refer to contributors.md
+ * Interested in contributing? Visit https://github.com/OpenRCT2/OpenRCT2
+ *
+ * OpenRCT2 is licensed under the GNU General Public License version 3.
+ *****************************************************************************/
+
+#include "StringReader.h"
+
+#include "../localisation/Localisation.h"
+#include "../util/Util.h"
+#include "String.hpp"
+
+UTF8StringReader::UTF8StringReader(const utf8* text)
+{
+    text = String::SkipBOM(text);
+
+    _text = text;
+    _current = text;
+}
+
+bool UTF8StringReader::TryPeek(codepoint_t* outCodepoint)
+{
+    if (_current == nullptr)
+        return false;
+
+    codepoint_t codepoint = String::GetNextCodepoint(_current);
+    *outCodepoint = codepoint;
+    return true;
+}
+
+bool UTF8StringReader::TryRead(codepoint_t* outCodepoint)
+{
+    if (_current == nullptr)
+        return false;
+
+    codepoint_t codepoint = String::GetNextCodepoint(_current, &_current);
+    *outCodepoint = codepoint;
+    if (codepoint == 0)
+    {
+        _current = nullptr;
+        return false;
+    }
+    return true;
+}
+
+void UTF8StringReader::Skip()
+{
+    codepoint_t codepoint;
+    TryRead(&codepoint);
+}
+
+bool UTF8StringReader::CanRead() const
+{
+    return _current != nullptr;
+}