This has still a few missing things, but this enough to start getting
some feedback. Missing are non qt projects, a solution for the
runconfiguration, a missing black line between the treeview on top and
the project settings at the bottom. Some flickering with removing/adding
widgets to the QScrollArea and not showing the expanded widget if the
Details button is right at the bottom.

It works, except that the code model doesn't get the rvct include
directories and defines yet. And you need to have everything for
rvct set up in your environment.

So now we use the values of the system environment as a backup
for build environment and system includes.

Task-number: 258468

older gcc does not automatically make nested classes of a friend class
friends as well.

QDir::cdUp() is strange ...

they were added to facilitate .prf exclusion from the project tree, but
that should be handled differently already.

that way they are auto-inherited by nested parsers, and it's the right
thing to do anyway.

... except where it is expected

fallbacks to values from the qt we were compiled/linked against really
make no sense.

almost too simple to be right, given the TODO ...

- parse .qmake.cache, remove workaround for not doing it
- look for the mkspecs in all the places qmake would do
- use the passed in properties instead of QLibraryInfo to find the qt
  data dir
- fix loading of generic features from within os-specific ones with the
  same name
- add multiple inclusion guard for features (including what seems to be
  a bug in qmake ...)
- misc cleanups and beautifications

qmake does so.
of course, in the longer run we need to get rid of this at all, but this
would require quite some reviewing of side effects.

to be able to share the option object among evaluators, it is passed by
pointer.

only field_sep stays static and becomes a string - that's effectively
just a cache to avoid repeated construction.

it's still static at that point, though.

non-inline implementations in a header? feh!

(the rest seems to have evaporated over time or never existed in the
first place)

it's redundand