StatusLabel: flickerless paint
PlaylistBar: drag and drop deeply nested folders

Support it.
Discard .ini cache when it's not being accessed

Refs #4193
Flush .ini cache after idle processing is done
Use the right prefix for bool variable
Construct CAppSettings in InitInstance()

It allows us to use COM objects in CAppSettings ctor.
FileAssoc: don't use static methods
FileAssoc: don't use static variables
Reduce header dependencies
Cosmetics

Placed 'extern' functions together.
Marked local functions as 'static'.
And some minor clean-ups and cosmetics.
Use 'override' keyword
A bit more sane hooks declaration
Simplify setting heap information