Change QList to QVector for speed increase

mLUT and mColorRampItemList are changed,
     for mLUT it shouldn't matter that much since an int is stored
     sequentially anyway, also in a QList,
     for mColorRampItemList it should make a difference,
     though it has to be converted from/to QList to keep API

src/core/raster/qgscolorrampshader.cpp

@@ -52,7 +52,7 @@ QString QgsColorRampShader::colorRampTypeAsQString()
 
 void QgsColorRampShader::setColorRampItemList( const QList<QgsColorRampShader::ColorRampItem>& theList )
 {
-  mColorRampItemList = theList;
+  mColorRampItemList = theList.toVector();
   // Reset the look up table when the color ramp is changed
   mLUTInitialized = false;
   mLUT.clear();
@@ -236,7 +236,7 @@ bool QgsColorRampShader::shade( double theRedValue, double theGreenValue,
 
 void QgsColorRampShader::legendSymbologyItems( QList< QPair< QString, QColor > >& symbolItems ) const
 {
-  QList<QgsColorRampShader::ColorRampItem>::const_iterator colorRampIt = mColorRampItemList.constBegin();
+  QVector<QgsColorRampShader::ColorRampItem>::const_iterator colorRampIt = mColorRampItemList.constBegin();
   for ( ; colorRampIt != mColorRampItemList.constEnd(); ++colorRampIt )
   {
     symbolItems.push_back( qMakePair( colorRampIt->label, colorRampIt->color ) );

src/core/raster/qgscolorrampshader.h

@@ -22,7 +22,7 @@ originally part of the larger QgsRasterLayer class
 #define QGSCOLORRAMPSHADER_H
 
 #include <QColor>
-#include <QMap>
+#include <QVector>
 
 #include "qgsrastershaderfunction.h"
 
@@ -63,7 +63,7 @@ class CORE_EXPORT QgsColorRampShader : public QgsRasterShaderFunction
     };
 
     /** \brief Get the custom colormap*/
-    QList<QgsColorRampShader::ColorRampItem> colorRampItemList() const {return mColorRampItemList;}
+    QList<QgsColorRampShader::ColorRampItem> colorRampItemList() const {return mColorRampItemList.toList();}
 
     /** \brief Get the color ramp type */
     QgsColorRampShader::ColorRamp_TYPE colorRampType() const {return mColorRampType;}
@@ -115,14 +115,14 @@ class CORE_EXPORT QgsColorRampShader : public QgsRasterShaderFunction
      * mDiscreteClassification holds if one color is applied for all values
      * between two class breaks (true) or if the item values are (linearly)
      * interpolated for values between the item values (false)*/
-    QList<QgsColorRampShader::ColorRampItem> mColorRampItemList;
+    QVector<QgsColorRampShader::ColorRampItem> mColorRampItemList;
 
     /** \brief The color ramp type */
     QgsColorRampShader::ColorRamp_TYPE mColorRampType;
 
     /** Look up table to speed up finding the right color.
       * It is initialized on the first call to shade(). */
-    QList<int> mLUT;
+    QVector<int> mLUT;
     double mLUTOffset;
     double mLUTFactor;
     bool mLUTInitialized = false;