[Development] [Request] Compiler warnings in Qt

[Kurt Pattyn]

When compiling applications with compiler flags on, a lot of warnings are generated for the Qt header files.
It needs a lot of work to exclude them in our builds, and some of them can just not be excluded because they are located in macros or inline methods.
The same holds for the moc generated code.

I propose to change the build system of Qt to enable as much compiler flags as possible and fail the build when there are any warnings.
Although most of them are more or less harmless, some could be potential errors (e.g. compiling with -Weffc++, generates a warning that the destructor of QSharedData is not virtual).

The public API could be a good starting point.

What do you think?