Randomly discovered during some other bug hunt, only with
AddressSanitizer on. Basically, ASAN detected stack-use-after-return
when playing with spinboxes in the Light Sources preferences when Qt
signal handlers tried to invoke lambda callbacks that referenced
deallocated stack memory.
The main problem is that those lambda functions in the constructor
were captruing by reference. When they were connected to Qt signals
and invoked after constructor completed, they accessed stack vars that
have gone out of scope.
So fixed that by changing lambda captures from `[&]` to explicit captures:
- [this] for lambdas needing only class member access
- [this, updateLight] for lambdas that need both class members and the
`updateLight` lambda.
"Professional CMake" book suggest the following:
"Targets should build successfully with or without compiler support for precompiled headers. It
should be considered an optimization, not a requirement. In particular, do not explicitly include a
precompile header (e.g. stdafx.h) in the source code, let CMake force-include an automatically
generated precompile header on the compiler command line instead. This is more portable across
the major compilers and is likely to be easier to maintain. It will also avoid warnings being
generated from certain code checking tools like iwyu (include what you use)."
Therefore, removed the "#include <PreCompiled.h>" from sources, also
there is no need for the "#ifdef _PreComp_" anymore
