Implement SH_Widget_Animation_Duration style hint

Summary:
Qt 5.10 deprecates the SH_Widget_Animate style hint in favor of a new
SH_Widget_Animation_Duration hint (see [1]).

If we are building against Qt 5.10 or newer, implement the new hint.

[1]: http://code.qt.io/cgit/qt/qtbase.git/commit/?id=04eba7b538072e2811f074bf66fd41f27c90b35c

Reviewers: hpereiradacosta

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D8759