doc: Fix several minor qdoc warnings

The fixes included undocumented enum values, which are now
marked as omitted, adding a test for Q_CLANG_QDOC for a
couple windows enum values, adding \fn commands for a pair
of member functions in QLocale, and a \fn command for an
obsolete function in QSqlError.

Change-Id: I12a8ea7287039096b9cfe7870d2ab213a3d78dcf
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/global/qnamespace.qdoc

@@ -1338,6 +1338,7 @@
     \omitvalue WA_WState_WindowOpacitySet
     \omitvalue WA_WState_AcceptedTouchBeginEvent
     \omitvalue WA_MacNoShadow
+    \omitvalue WA_ContentsMarginsRespectsSafeArea
 */
 
 /*! \typedef Qt::HANDLE

src/corelib/io/qsettings.h

@@ -88,7 +88,7 @@ public:
         NativeFormat,
         IniFormat,
 
-#ifdef Q_OS_WIN
+#if defined(Q_OS_WIN) || defined(Q_CLANG_QDOC)
         Registry32Format,
         Registry64Format,
 #endif

src/corelib/tools/qlocale.cpp

@@ -3806,6 +3806,12 @@ QString QLocale::toCurrencyString(double value, const QString &symbol, int preci
     return format.arg(str, sym);
 }
 
+/*!
+  \fn QString QLocale::toCurrencyString(float i, const QString &symbol) const
+  \fn QString QLocale::toCurrencyString(float i, const QString &symbol, int precision) const
+  \overload toCurrencyString()
+*/
+
 /*!
     \since 5.10
 

src/sql/kernel/qsqlerror.cpp

@@ -91,6 +91,7 @@ public:
 */
 
 /*!
+    \fn QSqlError::QSqlError(const QString &driverText, const QString &databaseText, ErrorType type, int number)
     \obsolete
 
     Constructs an error containing the driver error text \a