Fix clazy "detaching-temporary" warnings

From the clazy docs:

Finds places where you're calling non-const member functions on
temporaries. For example getList().first(), which would detach
if the container is shared.

src/core/qgsogcutils.cpp

@@ -3356,7 +3356,8 @@ QDomElement QgsOgcUtilsSQLStatementToFilter::toOgcFilter( const QgsSQLStatement:
   }
 
   // Process JOIN conditions
-  QString leftTable = node->tables().last()->name();
+  QList< QgsSQLStatement::NodeTableDef*> nodeTables = node->tables();
+  QString leftTable = nodeTables.at( nodeTables.length() - 1 )->name();
   Q_FOREACH ( QgsSQLStatement::NodeJoin* join, node->joins() )
   {
     QDomElement joinElem = toOgcFilter( join, leftTable );

src/providers/arcgisrest/qgsamsprovider.cpp

@@ -387,7 +387,7 @@ QgsRasterIdentifyResult QgsAmsProvider::identify( const QgsPoint & thePoint, Qgs
   queryUrl.addQueryItem( "imageDisplay", QString( "%1,%2,%3" ).arg( theWidth ).arg( theHeight ).arg( theDpi ) );
   queryUrl.addQueryItem( "mapExtent", QString( "%1,%2,%3,%4" ).arg( theExtent.xMinimum(), 0, 'f' ).arg( theExtent.yMinimum(), 0, 'f' ).arg( theExtent.xMaximum(), 0, 'f' ).arg( theExtent.yMaximum(), 0, 'f' ) );
   queryUrl.addQueryItem( "tolerance", "10" );
-  QVariantList queryResults = QgsArcGisRestUtils::queryServiceJSON( queryUrl, mErrorTitle, mError )["results"].toList();
+  QVariantList queryResults = QgsArcGisRestUtils::queryServiceJSON( queryUrl, mErrorTitle, mError ).value( "results" ).toList();
 
   QMap<int, QVariant> entries;
 

src/providers/grass/qgsgrass.cpp

@@ -942,7 +942,7 @@ QString QgsGrass::openMapset( const QString& gisdbase,
   QString processResult = QString( "exitStatus=%1, exitCode=%2, errorCode=%3, error=%4 stdout=%5, stderr=%6" )
                           .arg( process.exitStatus() ).arg( process.exitCode() )
                           .arg( process.error() ).arg( process.errorString(),
-                                                       process.readAllStandardOutput().data(), process.readAllStandardError().data() );
+                                                       process.readAllStandardOutput().constData(), process.readAllStandardError().constData() );
   QgsDebugMsg( "processResult: " + processResult );
 
   // lock exit code:

src/providers/grass/qgsgrassimport.cpp

@@ -435,8 +435,8 @@ bool QgsGrassRasterImport::import()
     // TODO: best timeout?
     mProcess->waitForFinished( 30000 );
 
-    QString stdoutString = mProcess->readAllStandardOutput().data();
-    QString stderrString = mProcess->readAllStandardError().data();
+    QString stdoutString = mProcess->readAllStandardOutput().constData();
+    QString stderrString = mProcess->readAllStandardError().constData();
 
     QString processResult = QString( "exitStatus=%1, exitCode=%2, error=%3, errorString=%4 stdout=%5, stderr=%6" )
                             .arg( mProcess->exitStatus() ).arg( mProcess->exitCode() )
@@ -713,8 +713,8 @@ bool QgsGrassVectorImport::import()
   QgsDebugMsg( "waitForFinished" );
   mProcess->waitForFinished( 30000 );
 
-  QString stdoutString = mProcess->readAllStandardOutput().data();
-  QString stderrString = mProcess->readAllStandardError().data();
+  QString stdoutString = mProcess->readAllStandardOutput().constData();
+  QString stderrString = mProcess->readAllStandardError().constData();
 
   QString processResult = QString( "exitStatus=%1, exitCode=%2, error=%3, errorString=%4 stdout=%5, stderr=%6" )
                           .arg( mProcess->exitStatus() ).arg( mProcess->exitCode() )

src/providers/ogr/qgsogrprovider.cpp

@@ -1229,7 +1229,7 @@ bool QgsOgrProvider::addFeature( QgsFeature& f )
           QgsDebugMsg( QString( "Writing string attribute %1 with %2, encoding %3" )
                        .arg( qgisAttId )
                        .arg( attrVal.toString(),
-                             mEncoding->name().data() ) );
+                             mEncoding->name().constData() ) );
           OGR_F_SetFieldString( feature, ogrAttId, mEncoding->fromUnicode( attrVal.toString() ).constData() );
           break;
 

src/providers/spatialite/qgsspatialitefeatureiterator.cpp

@@ -498,7 +498,7 @@ bool QgsSpatiaLiteFeatureIterator::getFeature( sqlite3_stmt *stmt, QgsFeature &f
       {
         if ( ic <= mRequest.subsetOfAttributes().size() )
         {
-          const int attrIndex = mRequest.subsetOfAttributes()[ic-1];
+          const int attrIndex = mRequest.subsetOfAttributes().at( ic - 1 );
           const QgsField field = mSource->mFields.at( attrIndex );
           feature.setAttribute( attrIndex, getFeatureAttribute( stmt, ic, field.type(), field.subType() ) );
         }