Adds Qt5 QIconLoader for the Qt5 build

The Qt5 versions of QIcon and QIconLoader fixed some of the Qt4 problems.
But... some are note:
    * xpm icon support;
    * Search icons in /usr/share/pixmaps as xdg standard states.

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Adds xpm icon support

Copied from the old QIconLoader.

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Honors /usr/share/pixmaps when searching for icons.

Author: Kaitlin Rupert <kaitlin.rupert@intel.com>
 Date: Aug 12, 2010
 Description: Make it so that the QIcon loader honors /usr/share/pixmaps
              directory.  This is a valid directory per the Freedesktop.org
              icon theme specification.
 Bug: https://bugreports.qt.nokia.com/browse/QTBUG-12874

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Merge branch 'use-qt5-qiconloader'

* use-qt5-qiconloader:
  Honors /usr/share/pixmaps when searching for icons.
  Adds xpm icon support
  Adds Qt5 QIconLoader for the Qt5 build