Doc: Point to the SG-10 SD-6 as a requirement for C++14 feature

Task-number: QTBUG-68702
Change-Id: I04b94079b6da48f39a82fffd153568f8dab3ef1b
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/global/qglobal.cpp

@@ -1037,6 +1037,11 @@ Q_STATIC_ASSERT((std::is_same<qsizetype, qptrdiff>::value));
 
     \snippet code/src_corelib_global_qglobal.cpp 53
 
+    \note Qt detects the necessary C++14 compiler support by way of the feature
+    test recommendations from
+    \l{https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations}
+    {C++ Committee's Standing Document 6}.
+
     \sa qConstOverload(), qNonConstOverload(), {Differences between String-Based
     and Functor-Based Connections}
 */

src/corelib/kernel/qdeadlinetimer.cpp

@@ -345,6 +345,11 @@ void QDeadlineTimer::setPreciseRemainingTime(qint64 secs, qint64 nsecs, Qt::Time
         deadline.setRemainingTime(250ms);
     \endcode
 
+    \note Qt detects the necessary C++14 compiler support by way of the feature
+    test recommendations from
+    \l{https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations}
+    {C++ Committee's Standing Document 6}.
+
     \sa setDeadline(), remainingTime(), hasExpired(), isForever()
 */
 

src/corelib/tools/qbytearraymatcher.cpp

@@ -366,6 +366,11 @@ int qFindByteArray(
     Since this class is designed to do all the up-front calculations at compile-time,
     it does not offer a setPattern() method.
 
+    \note Qt detects the necessary C++14 compiler support by way of the feature
+    test recommendations from
+    \l{https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations}
+    {C++ Committee's Standing Document 6}.
+
     \sa QByteArrayMatcher, QStringMatcher
 */