Move ensureUtf8Encoding to named namespace

To follow https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#sf21-dont-use-an-unnamed-anonymous-namespace-in-a-header

Add QtGlobal include to define QT_VERSION and QT_VERSION_CHECK macroses before
they're used.

apps/launcher/maindialog.cpp

@@ -308,7 +308,7 @@ bool Launcher::MainDialog::setupLauncherSettings()
                 return false;
             }
             QTextStream stream(&file);
-            ensureUtf8Encoding(stream);
+            Misc::ensureUtf8Encoding(stream);
 
             mLauncherSettings.readFile(stream);
         }
@@ -344,7 +344,7 @@ bool Launcher::MainDialog::setupGameSettings()
                 return {};
             }
             QTextStream stream(&file);
-            ensureUtf8Encoding(stream);
+            Misc::ensureUtf8Encoding(stream);
 
             (mGameSettings.*reader)(stream, ignoreContent);
             file.close();
@@ -544,7 +544,7 @@ bool Launcher::MainDialog::writeSettings()
 
     QTextStream stream(&file);
     stream.setDevice(&file);
-    ensureUtf8Encoding(stream);
+    Misc::ensureUtf8Encoding(stream);
 
     mLauncherSettings.writeFile(stream);
     file.close();

apps/wizard/mainwizard.cpp

@@ -165,7 +165,7 @@ void Wizard::MainWizard::setupGameSettings()
             return;
         }
         QTextStream stream(&file);
-        ensureUtf8Encoding(stream);
+        Misc::ensureUtf8Encoding(stream);
 
         mGameSettings.readUserFile(stream);
     }
@@ -197,7 +197,7 @@ void Wizard::MainWizard::setupGameSettings()
                 return;
             }
             QTextStream stream(&file);
-            ensureUtf8Encoding(stream);
+            Misc::ensureUtf8Encoding(stream);
 
             mGameSettings.readFile(stream);
         }
@@ -233,7 +233,7 @@ void Wizard::MainWizard::setupLauncherSettings()
             return;
         }
         QTextStream stream(&file);
-        ensureUtf8Encoding(stream);
+        Misc::ensureUtf8Encoding(stream);
 
         mLauncherSettings.readFile(stream);
     }
@@ -460,7 +460,7 @@ void Wizard::MainWizard::writeSettings()
     }
 
     QTextStream stream(&file);
-    ensureUtf8Encoding(stream);
+    Misc::ensureUtf8Encoding(stream);
 
     mGameSettings.writeFile(stream);
     file.close();
@@ -486,7 +486,7 @@ void Wizard::MainWizard::writeSettings()
     }
 
     stream.setDevice(&file);
-    ensureUtf8Encoding(stream);
+    Misc::ensureUtf8Encoding(stream);
 
     mLauncherSettings.writeFile(stream);
     file.close();

components/config/gamesettings.cpp

@@ -230,7 +230,7 @@ bool Config::GameSettings::isOrderedLine(const QString& line)
 bool Config::GameSettings::writeFileWithComments(QFile& file)
 {
     QTextStream stream(&file);
-    ensureUtf8Encoding(stream);
+    Misc::ensureUtf8Encoding(stream);
 
     // slurp
     std::vector<QString> fileCopy;

components/misc/utf8qtextstream.hpp

@@ -1,14 +1,16 @@
-#ifndef MISC_UTF8QTEXTSTREAM_HPP
+#ifndef OPENMW_COMPONENTS_MISC_UTF8QTEXTSTREAM_HPP
-#define MISC_UTF8QTEXTSTREAM_HPP
+#define OPENMW_COMPONENTS_MISC_UTF8QTEXTSTREAM_HPP
+
+#include <QtGlobal>
 
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 #include <QTextCodec>
 #endif
 #include <QTextStream>
 
-namespace
+namespace Misc
 {
-    void ensureUtf8Encoding(QTextStream& stream)
+    inline void ensureUtf8Encoding(QTextStream& stream)
     {
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
         stream.setCodec(QTextCodec::codecForName("UTF-8"));