Log Message:
Changes 5.5.1:

Qt Bluetooth
Bluetooth Low Energy API final release (5.4 was featuring tech preview).
Bluetooth Low Energy Support for Android (requires Android v18+) added.
Bluetooth Classic and Low Energy support for iOS and OS X.

Qt Core
You can now have Q_PROPERTY and Q_INVOKABLE within a Q_GADGET, and there is a \ 
way to query the QMetaObject of such gadget using the QMetaTYpe system.
Added Q_ENUM to replace Q_ENUMS which allow to get a QMetaEnum at compile time \ 
using QMetaEnum::fromType<T>. Such enums are now automatically registered \ 
as metatype, and can be converted to string within QVariant, or are printed as \ 
string by qDebug()

Qt GUI
Windows packages are all built with -opengl dynamic. No OpenGL-only or \ 
ANGLE-only builds are provided anymore.
On Windows the OpenGL implementation to use can now be configured based on the \ 
GPU vendor and driver version using JSON configuration files. This allows \ 
shipping fine-grained card and driver blacklists with the apps, when necessary.
QOpenGLWidget is now supported in iOS.
QImage: 8-bit alpha map and grayscale formats.
QImageReader: EXIF orientation can now be read though the transformation method, \ 
and applied on read to JPEGs if wanted.

Qt Multimedia
GStreamer 1.0 support. Note that the default is still 0.10. 1.0 support can be \ 
enabled by configuring Qt with '-gstreamer 1.0'.
New video filtering framework to integrate frameworks like OpenCV or compute \ 
APIs such as OpenCL or CUDA with VideoOutput elements.
New API to control camera viewfinder settings
Improved camera support on iOS (focus, zoom, exposure, viewfinder/image settings)
The QML MediaPlayer is now rendered in an OpenGL texture on iOS. This means \ 
VideoOutput supports advanced transformation, shader effects and doesn't have to \ 
be always on top of other items anymore.

Qt NFC
Neard based backend for Linux added.

Qt Network
New SSL back-end for iOS and OS X based on Secure Transport. Note that in Qt 5.6 \ 
this will become the default SSL: back-end on these platforms.
Support for libproxy
Support for TLS PSK ciphersuites
Support for elliptic curve certificates
Ability to select specific curves when using elliptic curve ciphersuites.

QPA
Added support for the Raspberry Pi 2.
Added support for the ODROID-XU3.
On supported desktops, the xcb plugin now uses the D-Bus based \ 
org.kde.StatusNotifier protocol for system tray icons, and \ 
org.freedesktop.Notifications for notifications.
KMS/DRM backend for EGLFS. This replaces the now deprecated KMS platform plugin. \ 
It allows running apps with eglfs on the console on systems with Mesa and \ 
devices that come with drm support.
EGLFS has a plugin-based backend mechanism in addition to the existing, \ 
statically compiled-in solution. Most compiled-in hooks are converted to be \ 
dynamically loaded plugins that are built based on configure time tests. This \ 
reduces the reliance on the device makespecs for RPi, i.MX6 and Mali-based \ 
devices.
Input handling is now unified for EGLFS and LinuxFB, avoiding the need to launch \ 
and configure LinuxFB-based apps differently than when using EGLFS.
tslib is now better integrated with EGLFS and LinuxFB to provide support for \ 
resistive single-touch touchscreens often used in industrial environments.
xcb is refactored to move GLX and EGL support into plugins. No more ifdefs, \ 
allowing building both backends.
Added a TUIO Touch plugin for receiving remote touch events via UDP.
Added a libinput plugin.
iOS: you can now use QFileDialog to browse system photos using a native image \ 
picker dialog by setting directory to QStandardPaths::PicturesLocation. Selected \ 
photos can be loaded using QFile.

Qt QML
It is now possible to conveniently expose custom C++ value types into the \ 
JavaScript environment of QML and QJSEngine.
Support for JavaScript typed arrays
Various performance improvements, notably QJSValue
Added convenience qJsEngine(QObject*) getter function.

Qt Quick
Windows now defaults to the threaded Qt Quick render loop when using desktop \ 
OpenGL (opengl32.dll).
QQuickWidget is now supported in iOS.
QQuickRenderControl supports threaded rendering.
Improved behavior of Flickable on OS X trackpads using pixel deltas from native \ 
gestures.
PinchArea handles native pinch gestures when the OS provides them (so far only \ 
on OS X). Otherwise it relies on touch events, as before.
Added a smart zoom signal to PinchArea to react to that gesture on an OS X trackpad.
MouseArea now has a scrollGestureEnabled property to control whether native \ 
scroll gestures from the OS will be handled by the wheel signal handler.

Qt Quick Controls
Qt Quick Extras (formerly Qt Quick Enterprise Controls) was added under the \ 
QtQuick.Extras import.
TreeView control for QAbstractItemModel-derived models. Supports \ 
QItemSelectionModel selection.

Qt WebEngine
Updated Chromium snapshot to version 40
WebEngineProfile for control of storage and cache paths and related policies.
Added support for javascript Geolocation API with QtLocation as a backend
Added API for managing downloading of files
Added API for controlling cache and cookie paths and policy
Added API for WebEngine settings
Added API for injecting user scripts
Various experimental QML API has been promoted to public
Added QtWebChannel integration API over Chromium IPC

Qt WebView
Added native implementations for Mac OS X.
Added API for running JavaScript (Requires API 19+ on Android).
Added API for setting the HTML content.
Added API for load status notifications.