Add Qt 5.5.1 changelog with updated 5.7 future direction notice

We should carry this in all 5.5.x and 5.6.x releases, to make sure
everyone gets the message. But for this release, we need to note the
changes from what was announced for 5.5.0:

Clang 3.2 cannot compile std::atomic properly, so it will not be
supported. That means the minimum XCode version we'll require will be
5.1, which fortunately does not raise the minimum OS X version that can
compile Qt. See http://llvm.org/bugs/show_bug.cgi?id=12670 for more
information.

ICC 14.x and 15.x on Windows miscompiles pointer-to-members across DLL
boundaries, so signal-slot connections fail. See QTBUG-40281.

Change-Id: I42e7ef1a481840699a8dffff1400a4377fcf4589
Reviewed-by: Lars Knoll <[email protected]>

dist/changes-5.5.1

@@ -0,0 +1,50 @@
+Qt 5.5.1 is a bug-fix release. It maintains both forward and backward
+compatibility (source and binary) with Qt 5.5.0.
+
+For more details, refer to the online documentation included in this
+distribution. The documentation is also available online:
+
+  http://doc.qt.io/qt-5.5/
+
+The Qt version 5.5 series is binary compatible with the 5.4.x series.
+Applications compiled for 5.4 will continue to run with 5.5.
+
+Some of the changes listed in this file include issue tracking numbers
+corresponding to tasks in the Qt Bug Tracker:
+
+  http://bugreports.qt.io/
+
+Each of these identifiers can be entered in the bug tracker to obtain more
+information about a particular change.
+
+****************************************************************************
+*                        Important Behavior Changes                        *
+****************************************************************************
+
+****************************************************************************
+*                          Future Direction Notice                         *
+****************************************************************************
+
+ - Qt 5.7 will begin requiring certain C++11 features in order to
+   compile. Due to bugs in the Clang compiler that comes with XCode 5.0,
+   that version will not be supported, despite what was noted in the Qt
+   5.5.0 changelog.
+   The minimum compiler versions for Qt 5.7 release will be:
+   * Clang 3.3 (XCode 5.1 contains version 3.4)
+   * GCC 4.7
+   * Intel C++ Composer XE 2013 SP1 (compiler version 14.0) on Linux and OS X
+   * Intel C++ Composer XE 2016 (compiler version 16.0) on Windows
+   * Microsoft Visual Studio 2012 (compiler version 17.0)
+
+****************************************************************************
+*                               Library                                    *
+****************************************************************************
+
+****************************************************************************
+*                      Platform Specific Changes                           *
+****************************************************************************
+
+
+****************************************************************************
+*                                Tools                                     *
+****************************************************************************