Fixes bugs where during project loading (observed with VST effects), empty
widgets and sub-windows would be left floating around. These were caused by
inconsistencies between the way VST UIs were created when loading a project
and when adding an effect in an existing project. In some situations, this
caused createUI to be called twice, leaving over multiple empty widgets.
This commit refactors some code in order to avoid creating unnecessary sub-
windows, which aren't needed with VST effects, but were still created,
usually being invisible. All sub-window related code was moved out of
VstPlugin into vestige.cpp, which is the only place where sub-window VSTs
are actually used. A new sub-class of VstPlugin, VstInstrumentPlugin, now
handles VST sub-windows and is used by vestigeInstrument.
"guivisible" attribute loading was moved out of VstPlugin as well and is
now done in VstEffectControls' and vestigeInstrument's loadSettings method
respectively. This causes some minor code duplication unfortunately.
Closes#4110
LMMS now properly builds and runs with Qt5. Various deprecated functions
had to be replaced like QString::toAscii()/fromAscii(). Also occurences
of FALSE/TRUE have been replaced with false/true.
LmmsStyle now derives from QProxyStyle and sets a style instance as base
style (Plastique for Qt4, Fusion for Qt5).
MOC files are not included anymore but added as regular source files.
What's missing is support for embedding VST plugins into a subwindow
inside LMMS on Linux/X11 due to missing QX11EmbedContainer class in Qt5.
Build instructions can be found in INSTALL.Qt5
Minimum version requirement for Qt4 has been raised to 4.6.0 for best
API compatibility between Qt4 and Qt5.
