QT Subsystem support

[t-harter]

Adds support for creating a QT version of the IDE. There are no big TODOs left right now but it still needs some testing. This is why this is a draft for now. Feedback is welcome.

To build with QT, just set the environment variable PB_QT=1 before compilation (make sure PB_GTK is not set as well). This will produce an executable called purebasic_qt.

Notes:

• Unfortunately it was not possible to do this in pure PB, so the QtHelpers.cpp is needed for some platform specifics. This means you need GCC and the QT devel packages to build this.
• The preferences files between the QT and GTK versions are not compatible (because all shortcut constant values differ). So either delete your preferences file or use a separate one with the -p option when starting the QT IDE.

[alphasnd]

Cool stuff ! May be you can change the name for the pref file when QT is active so it's easier to test

[alphasnd]

I successfully compiled and run the IDE on Ubuntu 22.04, it looks solid so far, very good work ! I noticed a crash on the Color chooser, last panel ('name') and using the scrollbar. I got a few refresh issue but it's probably due to VirtualBox, so I will test on a real box later. Will do some more tests and let you know, a very promising start !!

[alphasnd]

I will list the issues I found here:

• crash on the Color Chooser (tab name) when scrolling the name
• when using a Tree in the 'Explorer' tool, double cliking on a file do nothing
• the 'Help' window is properly displaying content, but there is no index and the << and >> button doesn't work
• Debugger -> Show Error log doesn't work (the error log is still visible)

[fantaisie-software]

Is it possible to rename the shortcut keys in the .prefs with '_qt' ? So we can use the same pref file for all the backends and I could merge it to have a live test for 6.20