For users

Fix old configure file loading in gtk2 version.
Thanks to Lars Wendler for noticing this.
Fix translucent background for close confirmation dialog in QtDesigner.
Workaround a Qt5 Bug and enable translucent background in Qt5.
Qt-Bug
Fix a lot of application misbehaviors and crashes for translucent background.
It should be safe to enable translucent background in almost all Qt4
applications.
Fix Qt menubar background when translucency is enabled.
Fix flash plugin when translucent background is enabled.
Improve shadow for QBalloonTip
Draw shadow at run time.
Fix chromium background color with custom background.
Gtk2: Workaround buggy signal handler in applications.
QtCurve-Bug
EasyTag-Bug

For packagers

A lot of old compile time options were removed. They are either for backward
compatibility (at compile time) or work around for bugs in drivers/libraries
that are not there anymore.
xcb-image dependency is removed (it is actually never used).
Relicense under LGPL. With permission from all contributors in the git log.
Qt5 version relies on the private headers. Please make sure the private
headers for QtWidgets are installed and a recompiling after a minor version
change in Qt5 may be necessary (since Qt does not grantee API stability
between minor versions).
Reorganize directories. qtcurve-utils is now lib/utils
Add libqtcurve-cairo for common drawing routines. This is only used by
the Gtk2 version (and may be used in Gtk3 version once there is a port).
Improve X11 dependency handling. The QTC_ENABLE_X11 option only have
effect on qtcurve-utils and qtcurve-utils with/without the option are
API and ABI compatible.