Reverted the update to the QWT 6.1 code to make QwtPlot::canvas()
return a QwtPlotCanvas -- it now returns QWidget.
This means our local copy of Qwt is the same as the published version
so we should be able to stop maintaining our own copy when Uwe pushes
the multiaxis stuff with 6.2.
Also fixed the LTM tooltip - the zoomer has been removed.
Porting the codebase to QT 5 (5.2) to get the
latest bug fixes, performance and improved platform
support.
This first part is to fixup the codebase to compile
on Qt 5, but some aspects have been broken (video).
The second part is to migrate from Qwt 6.0.1 to the
latest Qwt for multiaxis support.
The third part will be to fixup any platform specific
issues or issues identified at runtime.
There still some assert left in the code, but removed
a fair number of the examples where, its just as easy
to handle the condition gracefully, without crashing.
By 3.1 we will have eradicated assert from the code.
Upgrade to QWT 6.0.1, but still uses a locally patched copy
since support for 8 axes has not been included, despite it
being a relatively simple patch.
Fixes#634.
Fixes#567.
