Fix for Bug 352679 - QDir::cleanPath bug.

QDir::cleanPath does not seem to take into consideration symbolic
links when converting file names containing pointing to a relative
path.

For instance:
QDir::cleanpath(" /bin/../lib/gcc/x86_64-redhat-linux/5.1.1/../../
../../include/c++/5.1.1") returns "/include/c++/5.1.1" but this is
incorrect when /lib is a symbolic link pointing to /usr/lib
(Fedora 22 has this problem). Use instead
QFileInfo::.canonicalFilePath which seems to do the right thing.

Thanks to Claudiu Pop for the patch.

Differential Revision: https://phabricator.kde.org/D355